Viral Hepatitis — Questions

Likely cause. The picture is hepatitis B virus (HBV) reactivation precipitated by withdrawal of antiretroviral therapy (ART). South African first-line regimens (tenofovir plus lamivudine or emtricitabine, with efavirenz or dolutegravir) all contain two HBV-active agents, so ART was incidentally suppressing an undiagnosed or known HBV co-infection. Defaulting removed that suppression, HBV replication rebounded over years, and the eventual immune-mediated flare produced the raised ALT and jaundice.

Expected serology. HBsAg positive and anti-HBc total positive (lifelong exposure marker), with anti-HBc IgM low-positive possible in a severe flare. HBeAg may be positive or negative depending on phase, anti-HBe positive if HBeAg-negative, and HBV DNA very high, often above 10^7 IU/mL, with ALT typically above 5 times the upper limit of normal.

Management.

• Assess severity: full liver profile, HBV DNA, HBeAg/anti-HBe, HIV viral load and CD4, screen other hepatitides, and look for decompensation (encephalopathy, ascites, coagulopathy).
• Restart ART with a confirmed HBV-active backbone (tenofovir plus lamivudine or emtricitabine, plus dolutegravir). Both HBV-active agents must be continued indefinitely, and retained in any future regimen change, because stopping either reactivates HBV.
• Monitor closely: ALT, bilirubin and INR weekly initially, HBV DNA at baseline, week 4 and week 12, watching for an immune reconstitution flare as recovering immunity attacks infected hepatocytes.
• HCC surveillance six-monthly with AFP and ultrasound, and counsel that stopping ART again may be life-threatening; test and vaccinate contacts.

The per-percutaneous-exposure transmission risk is about 1.8% (range 0 to 7%), highest with hollow-bore needles.

a. Immediate wound care. Wash with soap and running water, allow to bleed, do not scrub or squeeze, and report to occupational health at once.

b. Workup of the source. Anti-HCV alone cannot separate active from resolved infection, so HCV RNA PCR is the determining test for transmission risk. Repeat HIV and HBV serology to exclude window-period infection, and document any prior HCV treatment, with consent and privacy safeguards.

c. Workup of the worker. Baseline within 48 hours: anti-HCV, HCV RNA, ALT, HIV, and HBV serology. The RNA is the earliest marker of acquisition. Check HBV immunity; because the source is HBsAg negative, HBIG is not needed, though a non-immune worker should complete the vaccine series.

d. Prophylaxis. There is no effective HCV post-exposure prophylaxis: immunoglobulin does not work and DAAs are not validated for this use. The pathway is surveillance with treatment if seroconversion occurs.

e. Surveillance. HCV RNA at week 4 for early detection, with anti-HCV, RNA and ALT repeated at weeks 12 and 24 (and HIV serology repeated). A positive RNA means acute HCV: refer for DAA therapy, which cures over 95% even in acute infection.

f. Reporting. Document on the occupational injury register and notify the Compensation Fund if seroconversion occurs.

a. Interpretation. A positive HCV total antibody at 2 days does not indicate infant infection. It almost always reflects passive transfer of maternal IgG anti-HCV across the placenta, which persists in the infant for up to 18 months. Vertical transmission is around 2 to 4% in HIV-negative mothers, rising to 10 to 25% with HIV co-infection, so most such infants ultimately test negative once maternal antibody clears.

b. Follow-up testing. The aim is to separate true infection from passive antibody:

• HCV RNA PCR at 2 to 6 months, the earliest diagnostic; a positive result at or after 2 months confirms transmission. Repeat a single negative, as early viraemia can be intermittent.
• Anti-HCV antibody at 18 months: persistence confirms the infant has made its own antibody, indicating true infection.
• ALT at each visit as a marker of liver inflammation.

c. Maternal and supportive care. Test the mother for HCV RNA (active viraemia defines the infant’s risk) and for HIV (co-infection raises transmission and follow-up intensity). Breastfeeding is not contraindicated unless the nipples are cracked and bleeding. Reassure the parents, and refer a confirmed case to paediatric hepatology, where pan-genotypic DAAs are licensed from age 3.

Phase. This is phase 4: HBeAg-negative chronic hepatitis (immune escape): historical HBeAg seroconversion followed by reactivated replication despite continuing anti-HBe positivity.

Supporting findings.

• Prior HBeAg seroconversion (HBeAg-positive two years ago, now anti-HBe positive), which should have delivered immune control.
• HBV DNA 8,500 IU/mL, above the 2,000 IU/mL phase 3 threshold, and rising over time (5,200 to 8,500), whereas phase 3 is a stable low steady state.
• Rising ALT from 28 to 62 U/L (above the male upper limit of 35 U/L), indicating active necroinflammation, where phase 3 has persistently normal ALT.

The underlying driver is usually a precore (G1896A) or basal core promoter (A1762T + G1764A) mutant abolishing HBeAg expression while allowing replication.

Remaining markers. Anti-HBc total positive (lifelong after natural infection, regardless of phase), and anti-HBc IgM negative or only low-positive (it marks acute infection; low-positive can appear in severe flares but is unusual here).

Phase 4 with this HBV DNA and ALT meets NDoH 2019 treatment criteria: start tenofovir or entecavir, usually lifelong, with continued six-monthly HCC surveillance.

(a) HBsAg+, anti-HBc total+, HBeAg+, anti-HBe-, HBV DNA 35,000 IU/mL. HBeAg-positive chronic HBV infection, either phase 1 (immune tolerant) or phase 2 (immune clearance); ALT and fibrosis distinguish them but are not given. Request ALT, APRI or FibroScan, HIV/HCV/HDV, AFP and ultrasound. Management: if phase 1 (normal ALT, no fibrosis, under 30), monitor 3 to 6 monthly. If phase 2 (raised ALT or significant fibrosis), treat with tenofovir or entecavir, since the viral load exceeds the 20,000 IU/mL threshold for HBeAg-positive disease.

(b) HBsAg-, anti-HBs+, anti-HBc total-. Vaccine-induced immunity: the recombinant vaccine contains only HBsAg, so anti-HBc is negative (it is positive after natural infection). No action required; confirm anti-HBs is at least 10 mIU/mL for documented protection.

(c) HBsAg+, anti-HBs+, anti-HBc total+, HBeAg-, anti-HBe+, HBV DNA 6,100 IU/mL, ALT 31 U/L. The simultaneous HBsAg and anti-HBs is unusual; the likeliest explanation is an HBsAg escape mutant (“a”-determinant, notably G145R) circulating while anti-HBs binds the wild-type epitope, with genotype reinfection or heterologous immunity as alternatives. The HBeAg-negative, anti-HBe-positive pattern with detectable HBV DNA and normal ALT fits phase 3 or early phase 4. Management: sequence the S gene and request quantitative HBsAg, confirm on a different assay platform, assess fibrosis, and repeat HBV DNA and ALT in 3 to 6 months; treat if HBV DNA exceeds 2,000 IU/mL with persistently raised ALT or at least F2 fibrosis.

An indeterminate result means the serum reacts with fewer than the full panel of HCV antigens the immunoblot needs to call a definite positive. The historical recombinant immunoblot assay required at least two of four bands (core, NS3, NS4, NS5); a single band was reported as indeterminate.

Three explanations exist:

• Resolved past infection with waned antibody breadth. HCV RNA is negative.
• Early or acute infection with a maturing response. HCV RNA may be positive.
• False-positive cross-reactivity to one antigen. HCV RNA is negative and the screen should be repeated on another platform.

HCV RNA polymerase chain reaction (PCR) is the decisive test: a positive result confirms active infection whatever the immunoblot shows, and a negative result excludes it. Modern algorithms have largely dropped the immunoblot in favour of direct RNA confirmation of any reactive screen.

HAV’s single open reading frame is translated as one polyprotein, which is then cleaved into the individual viral proteins.

The 3C protease (3Cpro) is the only viral protease HAV encodes, and it performs every internal cleavage of the polyprotein, producing both the structural (capsid) and non-structural proteins.

A small number of late cleavages are performed by host proteases instead, notably the final maturation cleavage of VP0 into VP4 and VP2 after RNA packaging.

The commercially available HAV vaccines are all inactivated whole-virus vaccines, differing in strain, manufacturer and antigen quantity.

Single-antigen products (all two-dose intramuscular schedules at 0 and 6 to 12 months):

• Havrix (GlaxoSmithKline; HM175 strain)
• Vaqta (Merck; CR326 strain)
• Avaxim (Sanofi Pasteur; GBM strain)

Combination product:

• Twinrix (GlaxoSmithKline): combined hepatitis A and hepatitis B (adult), three-dose schedule at 0, 1 and 6 months, or an accelerated four-dose schedule (0, 7, 21 to 30 days with a 12-month booster) for last-minute travellers. Must not be used for post-exposure prophylaxis (PEP): its HepA antigen dose is half that of the single-antigen formulations.

Live attenuated (H2 strain) vaccines are used in China and several Asian countries as single-dose schedules, and are not available in South Africa.

All inactivated formulations are aluminium-hydroxide adjuvanted, grown in human diploid cells, produce over 99% seroconversion after two doses, and are brand-interchangeable within a course. Long-term immunity is sustained for at least 25 years on serological follow-up.

Seroconversion is reduced in advanced cirrhosis, HIV with CD4 under 300 cells/µL, and post-transplant immunosuppression: a third booster dose at 6 to 12 months is recommended in these populations.

Co-infection is simultaneous acquisition of two viruses in a single exposure, seen most often in people who inject drugs. Superinfection is acquisition of a second virus in someone already chronically infected with the first; the dominant disease driver and the management depend on which virus is established and which is new.

Hepatitis C virus (HCV) suppresses hepatitis B virus (HBV) replication through core-protein-mediated downregulation of HBV transcription. In HBV/HCV co-infection one virus is usually clinically dominant, often with HBV suppressed. In HCV superinfection of chronic HBV, HCV drives the disease, HBV DNA often falls below detection while HBsAg persists, and fibrosis and HCC risk accelerate.

Treatment implications:

• Treat HCV with direct-acting antivirals (sofosbuvir-velpatasvir or glecaprevir-pibrentasvir), as in monoinfection.
• HBV reactivation after HCV cure is a recognised risk: clearing HCV lifts its suppression of HBV, so HBV DNA can rebound with severe flares.
• Screen every HCV-treated patient for HBsAg and anti-HBc. HBsAg-positive patients receive prophylactic tenofovir or entecavir from the start of direct-acting antiviral therapy and for 12 months after cure; anti-HBc-positive, HBsAg-negative patients have HBV DNA and ALT monitored during and after treatment.

Hepatitis B core-related antigen (HBcrAg) is a composite immunoassay marker measuring three overlapping hepatitis B virus (HBV) proteins together: HBeAg, HBcAg and the precore p22cr protein. Its clinical value is that it is the only widely available serum marker correlating with intrahepatic cccDNA transcriptional activity, giving a non-invasive surrogate for the persistence reservoir that would otherwise require liver biopsy.

Its main applications:

• Phasing chronic infection: highest in HBeAg-positive phases and falling progressively to the lowest levels in occult HBV, and identifying HBeAg-negative chronic hepatitis driven by precore or basal core promoter mutants (high HBV DNA and HBcrAg despite HBeAg-negativity).
• Predicting spontaneous HBeAg seroconversion, which falling HBcrAg often precedes by months.
• Predicting safe nucleos(t)ide analogue discontinuation: low end-of-treatment HBcrAg is associated with lower relapse.
• Predicting HCC risk independently of HBV DNA, with levels above ~4 log U/mL carrying higher long-term risk even when HBV DNA is suppressed.

Limitations are cost and availability (not in routine South African public-sector use or the NDoH 2019 guideline), and poor discrimination at very low cccDNA activity. HBcrAg therefore sits in the tertiary-care toolkit alongside quantitative HBsAg and HBV RNA, refining decisions on starting, stopping and HCC surveillance rather than screening.

Hepatitis A virus is Baltimore class IV: a positive-sense, single-stranded RNA virus in the family Picornaviridae, genus Hepatovirus.

A class IV genome can be translated directly by host ribosomes after entry, without a transcription step. In HAV this happens cap-independently, from an internal ribosome entry site (IRES) in the 5’ untranslated region (UTR).

Of the five clinically important hepatitis viruses, four are RNA viruses (HAV class IV, HCV class IV, HDV class V, HEV class IV) and one is a reverse-transcribing DNA virus (HBV class VII).

A reflex algorithm after an HBsAg-positive result must answer three questions: acute or chronic, which phase, and does the patient meet treatment criteria. The NDoH 2019 Viral Hepatitis Guideline sets out a tiered approach.

• Acute versus chronic: anti-HBc IgM (positive in acute, negative in chronic), with anti-HBc total to confirm exposure and exclude a false-positive HBsAg. IgM-positive acute disease enters an acute pathway with serial ALT and bilirubin monitoring.
• Phase the chronic infection: HBeAg and anti-HBe for HBeAg-positive versus HBeAg-negative phases, and HBV DNA quantification, the single most important marker for phase and treatment decisions (thresholds ~2,000 and ~20,000 IU/mL), with sex-specific ALT limits.
• Assess liver disease: full liver profile, platelets, and non-invasive fibrosis by APRI (AST to platelet ratio index) and FIB-4, the South Africa-preferred tests where FibroScan is unavailable; AFP and ultrasound for HCC surveillance.
• Screen co-infections: HIV, hepatitis C and hepatitis D, plus anti-HAV IgG to guide hepatitis A vaccination.
• Determine treatment eligibility: treat for cirrhosis or APRI above 2 (any DNA), HBeAg-positive disease with HBV DNA above 20,000 IU/mL and raised ALT or significant fibrosis, HBeAg-negative disease with HBV DNA above 2,000 IU/mL and raised ALT, HIV co-infection, pregnancy with HBV DNA above 200,000 IU/mL, or planned immunosuppression.

In resource-limited settings the highest-yield reflex is HBV DNA quantification (batched every 3 to 6 months for stable patients), HBeAg/anti-HBe can be once-per-patient after documented seroconversion, and APRI and FIB-4 add no reagent cost. The algorithm sorts patients into treat now, monitor, or investigate further (typically a HBV DNA/ALT discrepancy suggesting precore or basal core promoter mutants).

Mechanism. The dominant mechanism is immune-complex disease driven by chronic B cell stimulation. Chronic exposure of B lymphocytes to hepatitis C virus (HCV) antigens (E2 binding CD81; antigen drive in intrahepatic lymphoid follicles) produces polyclonal, then oligoclonal, then monoclonal expansion. The expanded B cells secrete rheumatoid-factor-like immunoglobulin M (IgM) that binds polyclonal immunoglobulin G (IgG), forming type II mixed cryoglobulins. These and conventional immune complexes deposit in small- and medium-vessel walls, glomeruli and the dermoepidermal junction, activating complement and recruiting neutrophils.

Four examples (any four):

1. Mixed cryoglobulinaemic vasculitis: palpable purpura (leukocytoclastic vasculitis), arthralgia, peripheral neuropathy, glomerulonephritis.
2. Membranoproliferative glomerulonephritis: renal immune-complex deposition with proteinuria, haematuria, hypertension and progressive impairment.
3. B cell non-Hodgkin lymphoma (typically marginal zone): late clonal expansion; ~5 to 10% of those with mixed cryoglobulinaemia progress to overt lymphoma.
4. Porphyria cutanea tarda: photosensitive bullous skin disease on sun-exposed surfaces, via reduced hepatic uroporphyrinogen decarboxylase activity.

Other recognised manifestations include lichen planus, a Sjögren-like sicca syndrome, autoimmune thyroiditis and type 2 diabetes. Direct-acting antiviral (DAA) cure regresses most extrahepatic manifestations, an argument for treatment regardless of fibrosis stage.

The hepatitis A capsid is built from four structural proteins: VP1, VP2, VP3 and VP4. Sixty copies of each assemble into a naked icosahedral capsid approximately 27 to 28 nanometres in diameter.

These proteins are not synthesised individually but released from a single polyprotein by sequential cleavage. The viral 3C protease performs most cleavages; a late maturation cleavage of VP0 into VP4 and VP2 (after RNA packaging) is performed by an unknown host protease.

TRUE.

The standard inactivated HAV vaccine schedule is two doses, a priming dose at time zero and a booster at six to twelve months, and applies in HIV-positive patients, including those with chronic liver disease. The vaccine is inactivated whole virus and safe at any CD4 count.

Response is reduced in advanced immunosuppression (around 52% to 94% seroconversion versus over 99% in immunocompetent adults), so a third booster dose six to twelve months after the first is commonly recommended in this population to improve seroconversion.

The HAV genome is approximately 7.5 kilobases (around 7,500 nucleotides) of positive-sense, single-stranded RNA. It has a single long open reading frame encoding a polyprotein of approximately 2,227 amino acids that is cleaved by the viral 3C protease into the structural and non-structural proteins.

The immune control phase (formerly “inactive carrier state”) is phase 3 of the AASLD/EASL five-phase classification: HBeAg-negative chronic infection with low replication and minimal liver injury. The expected markers:

ALT is also persistently normal, and histology shows minimal necroinflammation and fibrosis. Clinically this phase carries no immediate treatment indication (exceptions: cirrhosis at any DNA level, HIV co-infection, family history of HCC, or planned immunosuppression), but it is not benign: around 10% progress to HBeAg-negative chronic hepatitis (phase 4) over a decade, so serial HBV DNA and ALT monitoring continues, alongside six-monthly HCC surveillance from age 30. Sustained HBV DNA above 2,000 IU/mL with raised ALT signals progression and the need for treatment.

The defensible recommendation is the hepatitis B virus (HBV) birth dose, which South Africa subsequently adopted into the EPI in April 2020. The case rests on prioritising by disease burden, intervention efficacy, cost-effectiveness and the programmatic gap.

Disease burden favours HBV. HBV prevalence is ~6.7% in the general population and higher in HIV, and genotype A1 confers a roughly four-fold HCC risk in young Black men with early onset; hepatocellular carcinoma is a leading cancer death in this group. Vertical transmission is the principal route of chronic acquisition, with ~90% of perinatally infected infants becoming chronic and a quarter to 40% dying of cirrhosis or HCC. By contrast, primary varicella is largely self-limiting in healthy children, with severe disease concentrated in the immunocompromised.

The birth dose closes a window no other intervention covers. HBV is acquired at delivery and chronicity established within days, so the first hexavalent dose at 6 weeks is too late; only a dose within 24 hours interrupts it. A VZV programme would largely substitute for natural exposure most children already encounter.

Cost-effectiveness strongly favours HBV. The monovalent dose costs ~USD 0.20 and prevents decades of life lost, against ~USD 50 for VZV vaccine preventing a self-limiting illness. It is co-administrable with BCG and OPV already given at birth, minimising added cost.

International endorsement and a real gap. The WHO has recommended a universal birth dose since 2009, and Taiwan’s universal infant programme cut childhood HBsAg prevalence from 9.3% to 0.5% with sharp falls in childhood HCC. Until 2020 South Africa had no systematic perinatal HBV prevention, so the birth dose plus universal antenatal screening closes the major gap.

VZV vaccine would take priority only where HBV burden was low and already controlled, a universal birth dose was in place, and childhood varicella morbidity was high enough to justify a two-dose live-vaccine programme.

A complete answer makes the case for inclusion and situates it against current South African policy. The question framing pre-dates the April 2020 introduction of the monovalent birth dose, so it is best answered as the case for inclusion followed by the policy now in place.

The case for a birth dose

Mother-to-child transmission is the dominant route of chronic hepatitis B virus (HBV) acquisition in high-endemic settings. Without prophylaxis, vertical transmission runs at 70 to 90% from HBeAg-positive mothers and 10 to 40% from HBeAg-negative mothers, varying with maternal viral load. Around 90% of perinatally infected infants progress to chronic infection through HBeAg-induced immune tolerance, and a quarter to 40% of these die from cirrhosis or hepatocellular carcinoma (HCC) in adulthood.

HBV is acquired at delivery, and chronicity is established within days. The pre-2020 South African schedule gave its first dose at 6 weeks, far too late, and the vaccine takes 2 to 6 weeks to raise anti-HBs. Only a birth dose within 24 hours interrupts this window, preventing 85 to 90% of perinatal transmission, rising to ~95% with adjunctive hepatitis B immunoglobulin (HBIG) in HBeAg-positive infections.

The local burden justifies the intervention: HBsAg prevalence is ~6.7% in the general adult population and higher in HIV co-infection, and genotype A1 confers a roughly four-fold higher HCC risk in young Black men, presenting a decade or two earlier than in non-endemic settings.

Feasibility and cost

The monovalent vaccine costs ~USD 0.20 per dose, trivial against the lifetime cost of chronic hepatitis B, and can be co-administered with BCG and oral polio vaccine already given at birth. The WHO has recommended a universal birth dose since 2009 for any country with HBsAg prevalence above 2%, which South Africa exceeds. Universal dosing is cheaper and simpler than a targeted strategy, which would need universal antenatal screening with results available at delivery.

Current South African policy

Universal antenatal HBsAg screening entered the NDoH 2019 Viral Hepatitis Guideline, and a targeted monovalent birth dose entered the EPI in April 2020, given within 24 hours to infants of mothers who are HBsAg-positive or HBeAg-positive at screening. HBIG is reserved for infants of HBeAg-positive mothers on cost grounds, and maternal tenofovir is added from 28 to 32 weeks if HBV DNA exceeds 200,000 IU/mL. The remaining work is implementation: closing coverage gaps, returning antenatal screening results in time for delivery, and expanding HBIG supply.

A complete answer contrasts the host range, transmission, geography and clinical pattern of the two genotypes, and identifies the setting in which chronicity occurs.

Genotype 1

Genotype 1 is human-restricted and transmitted faeco-orally through contaminated water. It causes the large epidemic and endemic disease of Asia and Africa, affecting predominantly young adults. It produces acute, self-limited hepatitis in most people but is notably severe in pregnancy, where third-trimester infection causes fulminant hepatic failure with high maternal and fetal mortality. Genotype 1 does not establish chronic infection in immunocompetent hosts.

Genotype 3

Genotype 3 is zoonotic. Its reservoir is pigs, wild boar and deer, and humans are infected through undercooked meat (and occasionally through transfusion of blood components). It predominates in high-income settings in Europe, North America and parts of Asia, where it causes sporadic autochthonous (locally acquired) infection rather than waterborne epidemics. It affects older people, often with comorbidity, and is usually subclinical or mildly icteric.

Chronic infection

Chronic hepatitis E, defined as persistence of HEV RNA beyond three months, is caused almost exclusively by the zoonotic genotypes 3 and 4 in immunosuppressed hosts: solid-organ transplant recipients on calcineurin inhibitors, people with haematological malignancy or on chemotherapy, and advanced HIV. Genotypes 1 and 2 are not associated with chronicity. Chronic genotype 3 infection can progress to cirrhosis if untreated, yet often responds to reducing immunosuppression or to ribavirin.

India is a high-endemicity destination for HAV. The five-day departure window falls inside the two-week threshold beyond which single-dose HAV vaccine cannot be relied on to develop protective antibody before exposure.

The HAV prophylaxis

For a healthy adult traveller:

• HAV vaccine, single dose IM today (Havrix 1,440 ELU or Vaqta 50 U single-antigen), with a second dose on return to complete the two-dose schedule.
• HNIG intramuscular at a separate site for passive cover during the window before the vaccine response develops:
  • 0.02 mL/kg: about three months of protection.
  • 0.06 mL/kg: three to five months of protection.

HNIG matters most where worst-case protection counts: traveller over 40, immunocompromised, chronic liver disease, infant under 12 months, or any short-notice departure.

Wider travel consultation

Address the other travel exposures in the same visit: hepatitis E food and water precautions (no vaccine available in South Africa), hepatitis B (consider Twinrix on the accelerated schedule if non-immune), typhoid, routine vaccines up to date, malaria chemoprophylaxis and bite precautions by itinerary, and rabies or Japanese encephalitis for rural or prolonged stays.

A complete answer places HCV in Baltimore class IV, then walks the fully cytoplasmic cycle from receptor entry through the negative-strand intermediate to lipoprotein-coated progeny release.

Group

HCV is a class IV, positive-sense single-stranded RNA virus: the genome acts directly as a messenger RNA, sharing this property with the picornaviruses, togaviruses, and other flaviviruses.

Entry

The virion tethers to heparan sulfate proteoglycans, then binds CD81, the scavenger receptor B1, and the tight-junction proteins claudin-1 and occludin; the low-density lipoprotein receptor takes up the characteristic lipo-viro-particles via their host apoE and apoB coats. Clathrin-mediated endocytosis internalises the particle, and pH-dependent fusion in the endosome releases the genome.

Translation

An internal ribosome entry site (IRES) in the 5’ untranslated region recruits the 40S subunit without a cap, and the ~9.6 kb open reading frame is translated as one polyprotein of about 3,000 amino acids. Host signal peptidase cuts the structural junctions, the NS2/3 autoprotease cuts NS2/NS3, and NS3/4A cuts the downstream non-structural junctions, releasing 10 mature proteins.

Negative-strand intermediate

NS5B RNA-dependent RNA polymerase copies the genome into a short-lived, low-copy negative-strand intermediate within a membranous web induced by NS4B. NS5B lacks proofreading, so a quasispecies swarm arises that drives HVR1 immune escape and drug resistance.

Positive-strand progeny and exit

The negative strand templates many new positive-strand genomes, which are both translated and packaged by core protein at lipid droplets. Envelopment at the endoplasmic reticulum adds the E1/E2 spikes, and virions egress through the very-low-density lipoprotein (VLDL) pathway, emerging as lipo-viro-particles. The cycle is entirely cytoplasmic, with no DNA intermediate and no integration.

The approach has three steps: characterise the injury, work through the alternative aetiologies, and decide what needs urgent intervention.

Confirm and characterise

• Pattern of liver enzymes: hepatocellular (alanine aminotransferase [ALT]-dominant) versus cholestatic (alkaline phosphatase [ALP] and gamma-glutamyl transferase [GGT]-dominant) versus mixed.
• Severity: bilirubin, international normalised ratio (INR), albumin, glucose, lactate. INR above 1.5 with encephalopathy meets the working definition of acute liver failure and changes the urgency completely.
• Imaging: ultrasound with Doppler to exclude biliary obstruction and vascular causes.

Systematic differential

• Other viral: HEV (especially in returned travellers and with zoonotic exposure, the next-line test); cytomegalovirus (CMV), Epstein-Barr virus (EBV), herpes simplex virus (HSV) in the immunocompromised; HIV (always offer the test).
• Drugs and toxins: paracetamol (send a level on every patient), idiosyncratic drug-induced liver injury (DILI: anti-tuberculosis therapy, antibiotics, anticonvulsants, non-steroidal anti-inflammatory drugs), herbal and traditional medicines, recreational substances, Amanita mushrooms.
• Ischaemic hepatitis: shock liver, markedly raised lactate dehydrogenase (LDH), a hypotensive precipitant.
• Autoimmune hepatitis: antinuclear antibody (ANA), anti-smooth-muscle antibody, anti-liver-kidney-microsomal antibody type 1 (anti-LKM1), raised IgG.
• Wilson disease: consider in any patient under 40; Coombs-negative haemolytic anaemia, aspartate aminotransferase (AST) greater than ALT with ALT under 2,000, low alkaline phosphatase, low uric acid.
• Vascular: Budd-Chiari syndrome, portal vein thrombosis, veno-occlusive disease.
• Pregnancy-related: acute fatty liver of pregnancy (AFLP), the HELLP syndrome, intrahepatic cholestasis of pregnancy.
• Biliary obstruction: gallstones or malignancy, confirmed on imaging.

Urgent action

• Acute liver failure: contact the nearest transplant unit early; commence N-acetylcysteine (NAC) even in non-paracetamol acute liver failure.
• Specific antidotes: NAC for paracetamol, penicillamine for Wilson disease, aciclovir for suspected HSV.
• Stop the offending drug in suspected DILI.

The VITAMIN DEFG differential

• Viral (HEV, CMV, EBV, HSV, VZV, HIV-related opportunists)
• Ischaemic
• Toxins
• Autoimmune
• Metabolic (Wilson disease, haemochromatosis, alpha-1 antitrypsin deficiency)
• Idiosyncratic (drug-induced)
• Neoplastic infiltration
• Deposition (amyloid, sarcoid)
• Endocrine (thyroid storm, Addisonian crisis)
• Fetal liver (pregnancy-related)
• Granulomatous

Extrahepatic manifestations occur in around 20% of chronic hepatitis B virus (HBV) infection and arise predominantly from circulating immune complexes deposited in vascular beds, with a secondary contribution from cytokine-mediated injury. HBsAg-rich complexes lodge in vessel walls, glomeruli and serosa, activating complement and driving vasculitic damage.

Vasculitic and rheumatological

A serum-sickness-like prodrome of fever, arthralgia, urticaria and lymphadenopathy occurs in 10 to 20% during the late incubation or early acute phase, resolving as jaundice appears. HBV is the most important infectious cause of polyarteritis nodosa (PAN), a medium-vessel necrotising vasculitis presenting with abdominal pain, hypertension, mononeuritis multiplex and constitutional symptoms; treatment combines an HBV antiviral with plasma exchange and short corticosteroids, avoiding prolonged immunosuppression. A symmetric non-erosive arthritis, often part of the prodrome, may persist into the icteric phase.

Renal

Membranous nephropathy (children and young adults) presents with nephrotic syndrome and often remits spontaneously in children. Membranoproliferative glomerulonephritis (adults), frequently with cryoglobulinaemia, presents with proteinuria, haematuria and renal impairment. Biopsy shows viral antigens co-localised with IgG and C3. Management is antiviral plus supportive care, with immunosuppression generally avoided.

Other

Mixed (essential) cryoglobulinaemia (HBV accounts for ~5% of cases; HCV is commoner) presents with palpable purpura, arthralgia and neuropathy. Papular acrodermatitis of childhood (Gianotti-Crosti syndrome) is the prototypical acute-HBV skin eruption in children aged 1 to 6, self-limiting over weeks. Aplastic anaemia is a rare, probably immune-mediated complication weeks to months after acute HBV, with high mortality.

Approach

Any patient with new vasculitis, glomerulonephritis or atypical arthritis warrants HBV serology (HBsAg, anti-HBs, anti-HBc, HBV DNA) before immunosuppression, because immunosuppressing presumed primary autoimmune disease can precipitate severe HBV reactivation. Antiviral suppression with tenofovir or entecavir is the cornerstone and usually resolves the syndrome; plasma exchange and cautious, antiviral-covered immunosuppression are reserved for severe vasculitis or cryoglobulinaemia.

Both scenarios combine active and passive measures, but the neonatal aim is to interrupt vertical transmission before chronic infection is established, and the transplant aim is to prevent reactivation under profound immunosuppression.

(a) Neonate born to an HBsAg-positive mother

Without prophylaxis, transmission from HBeAg-positive mothers approaches 90% and over 90% of infected infants become chronic; combined active and passive prophylaxis prevents ~95% of cases.

• Antenatal (NDoH 2019): universal first-trimester HBsAg screening; if positive, quantitative HBV DNA, HBeAg and ALT. Maternal tenofovir from 28 to 32 weeks if HBV DNA exceeds 200,000 IU/mL, continued to 12 weeks postpartum if the only indication is transmission prevention.
• At birth: monovalent HBV birth-dose vaccine within 24 hours (10 micrograms intramuscular), co-administered with BCG and OPV, plus HBIG within 12 to 24 hours only if the mother is HBeAg-positive (the cost-rationed South African policy). EPI doses follow at 6, 10 and 14 weeks.
• Delivery and feeding: caesarean section is not indicated and breastfeeding is not contraindicated in a suppressed mother.
• Follow-up: post-vaccination serology (HBsAg and anti-HBs) at 9 to 18 months; anti-HBs of 10 mIU/mL or more confirms protection.

(b) HBsAg-positive patient before haematopoietic stem cell transplant (HSCT)

HSCT combines conditioning, prolonged neutropenia and graft-versus-host immunosuppression, and essentially all HBsAg-positive patients reactivate without prophylaxis, with high mortality.

• Pre-transplant: HBsAg and anti-HBc total (the latter to detect occult HBV, which still needs prophylaxis); if HBsAg-positive add HBV DNA, HBeAg/anti-HBe, fibrosis and HCC screening, with parallel HCV and HIV testing.
• Prophylaxis: entecavir or tenofovir (high genetic barrier), started before conditioning with HBV DNA ideally undetectable, and continued for at least 12 months after immunosuppression ends, often indefinitely given late-reactivation risk. Lamivudine is acceptable only for short courses at low baseline HBV DNA.
• Monitoring: HBV DNA and ALT every 1 to 3 months on treatment, and monthly for 3 months after stopping, watching for a severe late flare.

A complete answer separates the geographic epidemiology of the infection from the structural description of the genome, and links both to the dependence of hepatitis D virus (HDV) on hepatitis B virus (HBV).

Endemicity. HDV infects only people who are already hepatitis B surface antigen (HBsAg) positive, so its distribution is bounded by HBV prevalence but is far more geographically uneven. Roughly 5% of HBsAg carriers worldwide carry HDV, giving global estimates spanning about 12 million (the commonly cited figure) to 72 million (the higher modelled estimate), but prevalence clusters sharply into high-endemicity foci. Long-recognised hotspots include the Mediterranean basin, Eastern Europe, the Middle East (notably Pakistan and Iran), Mongolia, the Amazon basin of South America, and parts of Central and West Africa. In several of these settings 20 to 60% of HBsAg carriers are co-infected.

The pattern is dynamic. Universal infant HBV vaccination has reduced HDV prevalence in countries such as Italy by removing the susceptible HBsAg-positive pool, while migration has introduced new foci into low-prevalence regions of Northern and Western Europe. Eight genotypes (1 to 8) show geographic structure: genotype 1 is global, genotype 3 in the Amazon is associated with particularly severe disease, and genotypes 5 to 8 are largely African.

The genome. HDV has the smallest genome of any virus infecting humans: approximately 1.7 kilobases of circular, negative-sense, single-stranded RNA. Extensive internal base-pairing folds it into an unbranched rod-like structure. It contains a ribozyme, a self-cleaving RNA sequence that resolves the multimeric products of rolling-circle replication. The genome encodes a single protein, the delta antigen, produced in a small and a large form; host adenosine-deaminase RNA editing generates the large form. The virus carries no polymerase of its own and is replicated in the nucleus by host RNA polymerase II, and it borrows the HBsAg envelope of HBV to assemble infectious particles.

Hepatitis C virus (HCV) establishes chronic infection in 70 to 80% of exposed adults despite a vigorous innate and adaptive response. The paradox is resolved by integrated evasion at the innate, humoral, and cellular levels.

Innate immune evasion

NS3/4A cleavage of MAVS and TRIF. The NS3/4A serine protease cleaves both the viral polyprotein and two host interferon adaptors. Cutting MAVS (mitochondrial antiviral signalling protein) abolishes RIG-I/MDA5-driven IFN-β induction; cutting TRIF abolishes TLR3-driven induction. The infected hepatocyte cannot mount a type I interferon response. NS3/4A is also the target of the -previr drugs (glecaprevir, voxilaprevir). PKR inhibition. NS5A and E2 bind and inhibit protein kinase R (which phosphorylates eIF-2α to halt translation), preserving viral translation. Downstream sabotage. HCV induces SOCS1/SOCS3 and STAT1 hypomethylation, blunting JAK-STAT responses to interferon. ISG paradox. High pre-treatment intrahepatic ISG expression and plasma CXCL10 (IP-10) predict poor interferon-α response, reflecting a saturated, exhausted antiviral system; linked to the IFNL3 (IL28B) locus, where the rs12979860 CC genotype favours clearance and response. NK suppression. E2 cross-links CD81 on natural killer (NK) cells, inhibiting NK function and dendritic cell maturation.

Humoral evasion

HVR1 escape. Hypervariable region 1 of E2 is the immunodominant neutralising target and mutates within weeks under antibody pressure. Quasispecies. NS5B lacks proofreading (mutation rate ~10⁻⁴ to 10⁻⁵; about 10¹² virions per day), so escape variants pre-exist in the swarm. Glycan shielding of E1/E2 conserved epitopes and cell-to-cell spread further evade neutralising antibody.

Cellular evasion

CD4+ help failure is the hallmark of progression to chronicity: a broad, sustained CD4+ response predicts resolution, and its loss collapses CD8+ proliferative capacity. CD8+ exhaustion follows chronic antigen exposure, with PD-1, TIM-3, LAG-3 and CTLA-4 upregulation, lost cytokine production (IFN-γ, IL-2, TNF) and reduced cytotoxicity (as in chronic HBV, LCMV and cancer). CTL escape mutations in immunodominant epitopes expand in the quasispecies. Treg expansion in the liver dampens effector function. The core protein binds C1qR to directly inhibit T cells, and dendritic cell dysfunction (plasmacytoid and conventional) impairs interferon and antigen presentation.

The tolerogenic liver compounds these as a viral sanctuary. Because innate sensing, antibody and T cell arms are all disabled, sterilising immunity does not follow natural clearance (reinfection occurs in PWID, MSM and chimpanzees) and direct-acting antiviral (DAA) cure does not protect against reinfection, with direct implications for vaccine design and elimination.

The G1896A pre-core stop codon mutation is a single nucleotide change (TGG to TAG) creating a premature stop codon at codon 28 of the pre-core open reading frame. The pre-core protein is normally processed into secreted HBeAg, so the mutation abolishes HBeAg expression while leaving replication intact.

Its stability is genotype-dependent because position 1896 base-pairs with position 1858 in the epsilon stem-loop needed for pregenomic RNA encapsidation. In genotypes B, D and E (thymidine at 1858) the G1896A change strengthens the stem-loop and is selected; in genotype A (cytosine at 1858) it destabilises the stem-loop and is selected against. This is why precore-mutant chronic hepatitis is common in the Mediterranean, East Asia and sub-Saharan Africa but rare in genotype-A infection.

Functional significance: the patient appears HBeAg-negative on routine serology despite active replication, so the classical inverse correlation between HBeAg and viral load no longer holds. Loss of the HBeAg tolerogenic effect permits more aggressive immune-mediated injury, fluctuating ALT and higher HCC risk than wild-type at the same viral load, and spontaneous HBeAg seroconversion is no longer a meaningful endpoint, so patients usually need lifelong nucleos(t)ide analogue therapy.

Expected profile:

The basal core promoter mutation (A1762T + G1764A) produces the same HBeAg-negative phenotype through reduced transcription rather than a stop codon, and the two can co-exist; sequencing confirms the profile where available. Treat with tenofovir or entecavir, lifelong, with six-monthly HCC surveillance.

A complete answer states the current absence of a vaccine, the biological reasons it is uniquely hard, the strategies tried, and why a vaccine still matters despite curative therapy.

Current status

There is no licensed HCV vaccine after three decades of work. Curative direct-acting antivirals (DAAs) treat but do not prevent, and the World Health Organization 2030 elimination targets cannot be met in high-incidence groups, above all people who inject drugs (PWID), where reinfection after cure runs at 3 to 15% per year.

Why it is uniquely difficult

• Extreme diversity: eight genotypes at ~30 to 35% divergence, and a within-host quasispecies swarm from the proofreading-deficient NS5B polymerase.
• Hypervariable envelope: the immunodominant E2 HVR1 mutates under antibody pressure, so neutralising responses are routinely escaped.
• No sterilising immunity: reinfection after spontaneous clearance is well documented, undermining the classical correlate-of-protection model.
• Adaptive failure: CD4 help failure and CD8 T-cell exhaustion (PD-1, TIM-3, LAG-3) mark progression to chronicity.
• Tools: loss of the chimpanzee model leaves no tractable small-animal model, and correlates of protection remain ill-defined.

Strategies attempted

A T-cell vaccine (ChAd3-NSmut prime, MVA-NSmut boost) reached phase 2 in active PWID: safe and immunogenic, it reduced peak viraemia but did not prevent chronic infection. Recombinant E1/E2 subunit vaccines target neutralising antibody and are in early trials, and combination platforms aim to pair both arms. Controlled human infection models, now safer because DAAs can rescue any infected volunteer, could accelerate screening.

Why a vaccine is still needed

DAA cure gives no protective immunity, DAA and diagnostic access are uneven, and modelling argues elimination in PWID-driven epidemics is not feasible without one. The next generation will likely combine broadly neutralising antibody induction against the conserved CD81-binding site with polyfunctional T-cell responses, with mRNA multi-antigen platforms a promising delivery route. The strategic case has shifted from individual cure to interrupting transmission at the population level.

Hepatitis B virus (HBV) is the prototype of the Hepadnaviridae (Baltimore class VII), unusual in using reverse transcription despite being a DNA virus and in maintaining a persistent nuclear mini-chromosome that current treatment cannot eliminate.

Replication cycle and drug targets

Attachment and entry. Low-affinity binding to heparan sulfate proteoglycans is followed by high-affinity binding of the myristoylated preS1 region to NTCP (sodium taurocholate co-transporting polypeptide), encoded by SLC10A1, delivering the nucleocapsid by endocytosis. Target: bulevirtide, a preS1-derived peptide that blocks NTCP (licensed for hepatitis delta; limited in HBV monoinfection).

cccDNA formation. The relaxed-circular DNA (rcDNA) is repaired into covalently closed circular DNA (cccDNA), which assembles with histones into a mini-chromosome that is the persistence reservoir. Target: cccDNA itself, by CRISPR/Cas9, base editors or epigenetic silencing, all investigational.

Transcription. Host RNA polymerase II transcribes cccDNA into the 3.5 kb pregenomic RNA (pgRNA) and the surface, core, polymerase and HBx messages. Targets: small interfering RNA (siRNA) and antisense oligonucleotides (JNJ-3989, VIR-2218, bepirovirsen) degrade HBV transcripts, lowering HBsAg.

Encapsidation and reverse transcription. pgRNA and polymerase are packaged into nucleocapsids nucleated at the epsilon signal, and polymerase reverse-transcribes pgRNA into rcDNA. Targets: nucleos(t)ide analogues (NUCs) (tenofovir, entecavir) inhibit the polymerase reverse-transcriptase; capsid assembly modulators block encapsidation.

Assembly, egress and integration. Mature nucleocapsids either recycle to the nucleus to amplify cccDNA or are enveloped and secreted as Dane particles alongside vast excess subviral HBsAg, using the ESCRT pathway. HBV DNA integration (X and S sequences) is a replication side-product that continues HBsAg production and contributes to HCC.

Effect on viral markers

Novel agents: capsid assembly modulators lower HBV DNA but not HBsAg; siRNA and ASO reduce HBsAg by 1 to 2 log10, breaking the decoy; immune modulators (TLR7/8 agonists, PD-1 inhibitors, therapeutic vaccines) restore exhausted T cells; cccDNA-targeting tools alone could achieve complete cure.

Endpoints

Sustained virological response (HBV DNA undetectable), HBeAg seroconversion (allowing finite therapy in HBeAg-positive disease), functional cure (sustained HBsAg loss, the realistic ceiling) and complete cure (cccDNA eradication, not achievable). The self-replenishing cccDNA mini-chromosome is the principal barrier to cure, compounded by integrated HBsAg output and T cell exhaustion, which is why the pipeline combines direct-acting and immune-restorative strategies.

A complete answer covers what genotyping and RAS testing once decided, how the pan-genotypic era narrowed both, and how South Africa organises them.

Genotyping

Eight major genotypes (1 to 8) differ by ~30 to 35% at the nucleotide level. Historically genotype drove regimen choice and duration in the interferon and early direct-acting antiviral (DAA) era, and genotype 3 carries prognostic weight through steatosis and faster fibrosis. In the pan-genotypic era (sofosbuvir/velpatasvir, glecaprevir/pibrentasvir) routine pre-treatment genotyping is often unnecessary, retained mainly for treatment-failure work-up, surveillance, and distinguishing reinfection from relapse.

South African genotype distribution

South Africa is pan-genotypic with a distinctive signature: genotype 5a was first identified here and stays largely confined to southern Africa. In the general population genotypes 1 and 5 co-dominate, with genotype 4 rising; in people who inject drugs, genotype 1a (~73%) and 3a (~15%) dominate and genotype 5 has not been detected.

Resistance-associated substitutions

RAS are amino acid changes that reduce DAA binding or efficacy, present at baseline or selected during therapy.

NS5A RAS matter most because they persist for years off therapy, whereas sofosbuvir’s high genetic barrier makes NS5B resistance rare. RAS testing is mainly indicated after DAA failure, to guide retreatment; it is not needed before first-line pan-genotypic therapy.

South African operational context

Genotyping runs on the NHLS network and RAS testing is centralised at a single national reference centre using polymerase-gene sequencing, reserved for treatment failure and selected complex cases. Pre-treatment RAS testing is not routine, since pan-genotypic regimens hold high cure rates across baseline RAS profiles.

A complete answer names the responsible genotypes, quantifies the maternal and fetal risk, and gives the leading explanations for the severity.

The clinical problem

The waterborne genotypes 1 and 2 acquired in the third trimester can progress to fulminant hepatic failure. Genotype 1 is the most common and best-documented cause, but genotype 2 also poses a severe threat, with high maternal mortality and miscarriage rates reported during outbreaks. Maternal case-fatality in outbreak settings is high, in the order of 20 to 30%, far exceeding the mortality of hepatitis E in non-pregnant adults or of other acute viral hepatitides in pregnancy. Fetal and neonatal outcomes are also poor, with high rates of miscarriage, stillbirth, premature delivery and vertical transmission. This severity is a feature of the genotype 1 and 2 epidemics of Asia and Africa; the zoonotic genotype 3 of high-income settings does not show the same risk in pregnancy.

Proposed mechanisms

The reason for the exaggerated severity is not fully settled, but several contributing factors are recognised:

• Higher viral replication: pregnant women with hepatitis E tend to have higher HEV viral loads.
• Hormonal influence: the high oestrogen and progesterone levels of pregnancy modulate viral replication and the immune response.
• Immune adaptation of pregnancy: the shift away from a T-helper-1 response that protects the fetus may blunt antiviral immunity, allowing more severe hepatic injury.

Hepatitis E is therefore an important cause of maternal mortality during outbreaks, and supportive care with prompt recognition of acute liver failure is essential, since ribavirin is contraindicated in pregnancy.

A complete answer separates the serological and molecular tests, states their limitations, and explains why the strategy shifts in immunosuppression.

The immunocompetent patient

In an immunocompetent person with acute hepatitis, diagnosis rests first on serology:

• Anti-HEV IgM indicates recent infection and is the usual front-line test. Its sensitivity and specificity vary considerably between commercial assays, so a negative IgM does not fully exclude infection and a single positive may need confirmation.
• Anti-HEV IgG rising or seroconverting between paired samples supports recent infection; a single IgG reflects past exposure.
• HEV RNA by reverse transcription polymerase chain reaction (RT-PCR) in serum or stool confirms active infection and is useful early, before antibodies appear, and where serology is equivocal.

The immunosuppressed patient

Serology is unreliable in immunosuppression because the patient may not mount a detectable antibody response, so anti-HEV IgM and IgG can be falsely negative despite active infection. Diagnosis therefore depends on HEV RNA detection in serum and stool, which is the reference test in this group. An HEV antigen assay is an alternative marker where available. Because chronic hepatitis E is defined by persistence of HEV RNA beyond three months, repeat RNA testing is used both to make the diagnosis of chronicity and to monitor the response to reduced immunosuppression or ribavirin. Every transplant or haematology patient with unexplained persistently deranged liver enzymes should be tested for HEV RNA.

A complete answer traces the agent from non-A non-B hepatitis (NANBH) defined by exclusion, through the chimpanzee studies, to the 1989 molecular cloning and the 2020 Nobel Prize.

The pre-discovery era

Once assays for hepatitis A and hepatitis B existed, a chronic transfusion-associated hepatitis remained that neither could explain, and it was labelled non-A non-B hepatitis. Post-transfusion rates reached up to one in three in open-heart surgery, and many recipients progressed to cirrhosis and hepatocellular carcinoma. Harvey Alter led prospective transfusion-recipient cohorts showing an infectious bloodborne agent distinct from HAV and HBV, with a long incubation and a high rate of chronicity.

Chimpanzee transmission and physical characterisation

Chimpanzees were the only permissive model. Serial inoculation showed the agent was filterable at 30 to 60 nanometres, inactivated by chloroform (an envelope), and inactivated by solvent-detergent treatment of blood products. These properties pointed to a small enveloped RNA virus, though it could not be cultured.

Molecular cloning, 1989

Michael Houghton’s team at Chiron built a complementary DNA library from high-titre chimpanzee plasma and screened it with serum from a chronic NANBH patient. After roughly a million clones, clone 5-1-1 bound patient antibody but not control serum. Two 1989 Science papers reported the agent, now named hepatitis C virus, and the clone became the first anti-HCV ELISA, deployed for blood-donor screening from 1990.

Rice and the Nobel Prize

Charles Rice proved the cloned genome was infectious and built the replicon and JFH-1 cell-culture systems that underwrote direct-acting antiviral discovery. In October 2020 the Nobel Prize in Physiology or Medicine went jointly to Alter, Houghton, and Rice.

A complete answer explains why current treatment suppresses but does not cure hepatitis B virus (HBV), then maps the cure pipeline onto the specific viral and immune barriers.

Three levels of cure are recognised: sustained virological response (HBV DNA undetectable on therapy, achievable now but not curative), functional cure (sustained HBsAg loss off therapy, the realistic target, reached in 3 to 7% on pegylated interferon-alpha and ~1% per year on tenofovir), and complete cure (cccDNA eradication, not achievable with any current agent).

Viral factors

The covalently closed circular DNA (cccDNA) mini-chromosome is the central barrier: a stable nuclear form that is the template for all viral transcripts, self-replenishing through nucleocapsid recycling, and untargeted by any licensed drug. Integrated HBV DNA cannot replicate but continues producing HBsAg and HBx indefinitely, so even a perfect cccDNA-clearing agent may leave residual HBsAg. Massive HBsAg over-production as subviral particles floods the circulation at 1,000 to 10,000 times the concentration of complete virions, acting as a decoy that exhausts HBV-specific B and T cells. Genotype heterogeneity (ten genotypes, A to J) and precore/basal core promoter mutants further modify antigen expression and immune visibility.

Immunological factors

Chronic antigen exposure drives HBV-specific T cell exhaustion, with upregulation of the inhibitory receptors PD-1, TIM-3, LAG-3 and CTLA-4 and loss of effector function, so the response cannot clear infection even under pharmacological suppression. Soluble HBeAg acts as a tolerogen, crossing the placenta to induce neonatal tolerance and dampening T cell costimulation. HBV also achieves innate immune evasion, with HBx and polymerase inhibiting the MAVS, IRF3/7 and STAT1 signalling that would drive type I interferon, earning it a “stealth virus” reputation. Regulatory T cell expansion, myeloid-derived suppressor cells and NK cell dysfunction reinforce the immunosuppressive intrahepatic environment.

The cure pipeline

The likely route to functional cure is combination therapy: an HBsAg-lowering agent (small interfering RNA or antisense oligonucleotide, such as bepirovirsen, VIR-2218 or JNJ-3989) to break the decoy effect, paired with an immune restorer (PD-1 checkpoint inhibitor, TLR7/8 agonist or therapeutic vaccine) to let the host clear residual cccDNA-expressing hepatocytes. Capsid assembly modulators and entry inhibitors (bulevirtide) reduce cccDNA replenishment, while direct cccDNA-targeting tools (CRISPR/Cas9, base editors) remain investigational and are the only strategies that could achieve complete cure.

Each reflex should earn its cost by changing a decision. The five listed vary from essential to near-useless.

• Anti-HBs: drop. HBsAg and anti-HBs cannot coexist in typical infection, and the only exception (S-gene escape mutants such as G145R) is diagnosed by HBV DNA and sequencing, not anti-HBs. It is a useful reflex when HBsAg is negative (immunity versus susceptibility), but not when HBsAg is positive.
• Anti-HBc total: keep. It confirms genuine exposure, excludes a false-positive HBsAg, and is a required baseline before HCV direct-acting antivirals, rituximab or chemotherapy. Inexpensive and useful.
• Anti-HBc IgM: keep. It separates acute (positive) from chronic (negative) infection and flags severe flares, changing the monitoring and treatment pathway.
• HBeAg and anti-HBe: keep, but once per patient. Essential for phasing and treatment, but once HBeAg-negative, anti-HBe-positive seroconversion is documented, repeating adds little unless an unexpected HBV DNA rise or ALT flare prompts reassessment. A once-per-patient strategy saves substantial cost in follow-up.

Two gaps should be closed. HBV DNA quantification, the single most important treatment-decision marker, is absent and should be added as a reflex whenever HBsAg is positive in a treatment-evaluation setting. APRI (AST to platelet ratio index) and FIB-4 should be auto-reported, since both are calculated free from the full blood count and liver profile already requested and inform the treat-or-not decision under NDoH 2019.

The net effect is broadly cost-neutral: dropping anti-HBs and reducing repeat HBeAg/anti-HBe frequency offsets adding HBV DNA, while sharply improving information yield and alignment with the guideline’s treatment criteria.

Occult hepatitis B infection (OBI) is the persistence of HBV DNA in liver (and sometimes serum, usually below 200 IU/mL) despite an undetectable HBsAg by standard assays (Taormina 2008 consensus). It is seropositive (~80%, anti-HBc and/or anti-HBs detectable, resolved infection with cccDNA persistence) or seronegative (~20%, HBV DNA only).

Mechanisms

Three routes produce OBI: true low-level chronic infection where a small cccDNA pool supports HBsAg output below the assay threshold (the commonest); S-gene escape mutants (notably G145R in the “a” determinant) that replicate actively but evade the detection epitope, important in transfusion medicine; and co-infection-mediated suppression by HCV or HIV, with HBV rebound when the co-infection is treated.

Clinical importance

• HCC risk persists, probably through integrated HBV DNA and HBx, with HBV sequences found in 50 to 70% of HBsAg-negative HCC in endemic regions.
• Transfusion transmission drove the adoption of HBV nucleic acid testing (NAT) alongside HBsAg screening, including in South Africa.
• Anti-HBc-positive donor organs (especially livers) transmit HBV, so recipients receive lifelong antiviral cover.
• Immunosuppression-driven reactivation is the key pitfall: rituximab, allogeneic haematopoietic stem cell transplant (HSCT) and other profound immunosuppression can reactivate OBI with severe, sometimes fatal hepatitis, occurring months after treatment ends.

Management (NDoH 2019)

Screen anti-HBc total alongside HBsAg and anti-HBs before high-risk immunosuppression. Treat detectable HBV DNA as HBsAg-positive disease with tenofovir or entecavir. Where HBV DNA is undetectable but anti-HBc positive, give prophylactic NUC before rituximab or allogeneic HSCT and for at least 12 months afterwards, with HBV DNA and ALT monitoring; anti-HBc-positive HSCT recipients always receive prophylaxis because late-reactivation risk is too high to leave unguarded.

Chronic hepatitis C virus (HCV) drives a spectrum of B cell disorders from benign polyclonal expansion through mixed cryoglobulinaemia to overt B cell non-Hodgkin lymphoma (NHL).

Pathogenesis. The dominant mechanism is chronic B cell stimulation by HCV antigens: E2 binds CD81 on B lymphocytes, driving polyclonal then oligoclonal then monoclonal expansion. A subset acquires further genetic lesions (most often t(14;18) BCL2 rearrangement) and progresses to lymphoma.

Spectrum. Polyclonal expansion, then type II mixed cryoglobulinaemia, then marginal zone lymphoma (splenic, nodal, or extranodal; the commonest HCV-associated NHL), and less often lymphoplasmacytic lymphoma or diffuse large B cell lymphoma (usually transformation of indolent disease). Around ~5 to 10% of those with mixed cryoglobulinaemia progress to overt lymphoma.

Clinical features. B symptoms, lymphadenopathy, splenomegaly, cytopaenias, extranodal disease (parotid, stomach, skin).

Diagnosis. Tissue biopsy with histology, flow cytometry and cytogenetics. Screen all newly diagnosed B cell NHL for HCV, and HCV-associated cases for human immunodeficiency virus (HIV) and hepatitis B virus (HBV) before any rituximab (the highest-risk drug for HBV reactivation).

Treatment. Direct-acting antiviral (DAA) therapy regresses indolent HCV-associated lymphomas (notably splenic marginal zone lymphoma), with a haematological response in around half. Combined DAA plus rituximab is standard for aggressive disease, with mandatory tenofovir or entecavir prophylaxis in any HBsAg- or anti-HBc-positive patient.

A complete answer covers the genotypes circulating in Africa, the epidemiological pattern (endemic seroprevalence versus explosive outbreaks), the populations most affected, and the public-health response.

Genotypes and transmission

Africa is dominated by the human-restricted genotypes 1 and 2, transmitted faeco-orally through water contaminated with human sewage. Genotype 1 circulates across much of sub-Saharan Africa and North Africa; genotype 2 was first described in Mexico but also occurs in West Africa (Nigeria, Chad). These contrast with the zoonotic genotypes 3 and 4 of high-income settings, which are acquired from undercooked pork and game and are uncommon in Africa.

Endemic burden and outbreaks

Hepatitis E virus (HEV) shows high background seroprevalence in many African populations, reflecting widespread exposure through unsafe water. Superimposed on this are large waterborne epidemics, characteristically where sanitation breaks down. Outbreaks have been recorded in Namibia and in refugee and internally-displaced-person camps across sub-Saharan Africa (for example in South Sudan, Chad, and Uganda), often during the rainy season when latrines flood.

Populations at greatest risk

The defining feature of genotype 1 disease is its severity in pregnant women, particularly in the third trimester, where it causes fulminant hepatic failure with case-fatality of ~20 to 30% and high rates of fetal loss and stillbirth. This makes HEV a major cause of maternal mortality during African outbreaks.

South African data

South African seroprevalence has ranged widely, from ~2 to 43% in studies between 1990 and 2020, concentrated in Gauteng and the Western Cape and rising with age. Early surveys among canoeists, students, and rural and urban community participants pointed to contaminated water as the probable exposure, though they relied on older, less reliable assays. More recent Western Cape work tells a zoonotic story: the first Southern African genotype 3 case was described in 2013 in an HIV-positive person, followed by a case in a transplant recipient, and blood-donor cohorts have shown seroprevalences of around ~25 to 28% with pork consumption as a significant risk factor and a fulminant genotype 3 liver-failure case reported. Hepatitis E virus RNA has been detected in local pig herds and in pork products in Cape Town, supporting foodborne transmission, while a single RNA-positive genotype 3 donation was found among 10,000 screened blood donations. Seroprevalence among pregnant women in Pretoria was low, at ~3%.

Public-health response

Control rests on water, sanitation, and hygiene: securing safe drinking water, sanitary excreta disposal, and case isolation during outbreaks. The licensed recombinant vaccine is manufactured and used in China and is not yet deployed in African programmes, though it has been considered for outbreak use in high-risk groups. Diagnosis in outbreaks relies on anti-HEV IgM serology, with HEV RNA confirmation where laboratory capacity allows.

The discordance is unidirectional (new positive, old negative), so the answer weighs the competing explanations and then sets out a staged resolution.

Possible causes

True positives the old assay missed. The new platform may be more sensitive (a third-generation design detecting core, NS3, NS4 and NS5), or the samples were taken in the window period with antibody below the old cut-off. This is the most clinically important possibility, because the new assay is right.

False positives from the new assay. Lower specificity at the current cut-off, non-specific binding in autoimmune disease, rheumatoid factor or heterophile antibody cross-reactivity, or miscalibration.

Sample-related. Storage degradation at minus 20 (rather than minus 70), freeze-thaw effects, contamination or plate carry-over from high-positive wells, or mislabelling.

Reagent and operational. Lot variability, calibrator drift, plate-edge effects, operator error. Rarely, an original false-negative on the day.

Investigation

• Repeat the 10 samples in duplicate on the new platform with known controls, and inspect QC charts for run excursions.
• Cross-platform comparison on at least one alternative anti-HCV assay to triangulate the true status.
• HCV RNA nucleic acid testing as the decisive marker: a positive resolves the discrepancy in favour of the new assay, while a negative does not exclude resolved past infection. HCV core antigen is a secondary virological marker.
• Clinical and risk-factor review of the 10 patients, and a fresh sample where possible to exclude storage artefact.
• Recompute sensitivity and specificity against a corrected reference (RNA plus cross-platform agreement).

Conclusion

If most discordants are RNA-confirmed, the new assay has improved sensitivity and should be adopted with reflex RNA confirmation. If most are RNA-negative and negative elsewhere, it has a specificity problem needing recalibration or rejection. The 100% concordance on the 50 known positives confirms acceptable sensitivity, so the decision rests on specificity.

The vignette describes hepatitis D superinfection: hepatitis D virus (HDV) acquired by someone with established chronic hepatitis B virus (HBV), signalled by long-standing hepatitis B surface antigen (HBsAg) positivity with HDV RNA appearing for the first time. Superinfection lands on a fully supported HBV background, so the delta virus chronifies in about 70 to 90% of cases (option C), the most rapidly progressive form of chronic viral hepatitis, with accelerated fibrosis and a raised risk of cirrhosis and hepatocellular carcinoma.

This is separated from co-infection, where HBV and HDV are acquired together: that behaves like an acute hepatitis B, self-limited in about 95% of immunocompetent adults, with chronic hepatitis D in under 5% (options A and B describe co-infection, not the scenario asked). Option D understates the outcome, and option E overstates it, since the dominant long-term problem of superinfection is chronicity, not near-universal fatal liver failure. New or worsening hepatitis in a known HBsAg carrier should prompt testing for HDV.

HBeAg positive, very high HBV DNA (10^9 IU/mL) and normal ALT identify phase 1: HBeAg-positive chronic infection (immune tolerant). This is typical of adults infected vertically, in whom placental HBeAg induced neonatal tolerance, allowing decades of high replication without immune-mediated injury.

Phase 2 (B) would show elevated ALT; phases 3 and 4 (C, D) require HBeAg negativity; phase 5 (E) requires HBsAg negativity. Phase 1 patients are generally not treated in South Africa, except adults over 30 with HBV DNA above 1,000,000 IU/mL plus significant fibrosis; six-monthly HCC surveillance still applies.

Impending immunosuppression is one of the situations in which the guideline says to treat regardless of ALT, HBV DNA or HBeAg. B cell depletion with rituximab, cytotoxic chemotherapy and transplant conditioning all carry a high risk of hepatitis B reactivation, which can be fulminant. Antiviral cover is started before the immunosuppression, not in response to a later flare.

The other triggers in this “treat regardless” group are cirrhosis (compensated or decompensated), an APRI score above 2, and acute liver failure.

Options A and B apply the ordinary viral-load and ALT thresholds, which are the wrong frame here: the point of prophylaxis is to act before reactivation, not to wait for it. Immunoglobulin (D) has no role in this setting, and the serology is unambiguous, so repeating it (E) only wastes time.

HAV remains a self-limiting acute infection even in profound immunosuppression. There is no chronic carrier state, including in post-transplant patients, advanced HIV, and severe combined immunodeficiency (SCID).

The transplant recipient may have a longer or more severe acute illness because of reduced hepatic reserve and the immunosuppressive regimen, but the virus is cleared and immunity is preserved long-term. Management is supportive, with hepatology and transplant-unit involvement for severe disease.

Acute HAV superimposed on chronic liver disease, particularly chronic hepatitis C, carries a substantially increased risk of fulminant hepatic failure. The chronic-HCV liver has reduced hepatic reserve, and the immune response that mediates HAV liver injury can precipitate decompensation rather than self-limited recovery. This is the rationale for routinely vaccinating patients with chronic liver disease against HAV.

The other options are wrong: HAV does not cause chronic carriage, does not recombine with HCV, and does not produce prolonged infectious faecal shedding.

Genotype 3 hepatitis E is zoonotic. Its animal reservoir is pigs, wild boar and deer, and humans acquire it by eating undercooked meat (pork products, game, and occasionally shellfish that have concentrated the virus). It causes sporadic autochthonous (locally acquired) infection in high-income settings, which is why this patient has no travel history. Transfusion-transmitted HEV from viraemic blood donors is the recognised secondary route, and has prompted donor screening in several countries.

A describes the genotype 1 and 2 waterborne route of Asian and African epidemics, not genotype 3. B describes the bloodborne and sexual routes of hepatitis B and C; HEV spreads this way only through transfusion. D overstates vertical transmission, which matters for genotype 1 in pregnancy but is not the dominant route for genotype 3. E is incorrect: HEV is not a respiratory pathogen.

Anti-HBs below 10 mIU/mL defines a non-responder, and the first step is a single booster dose with a recheck; if it stays below 10 mIU/mL, give a complete second three-dose series. A single booster rescues 25 to 50% of initial non-responders, so it is tried before committing to a full second course. Always check HBsAg first to exclude undiagnosed chronic infection as the reason for apparent non-response.

Documenting protection (A) is wrong because 4 mIU/mL is below threshold. A single sub-threshold titre does not define a permanent non-responder (C). There is no live-attenuated HBV vaccine (D); all are recombinant subunit. The 80 microgram single dose (E) is not a standard schedule; the correct next step is a 20 microgram booster then a full re-course if needed. Haemodialysis patients are the exception, receiving 40 microgram doses with annual anti-HBs testing.

For a healthy, immunocompetent adult aged 1 to 40 within the 14-day post-exposure window, the recommended post-exposure prophylaxis (PEP) is single-dose HAV vaccine alone.

The stratified algorithm:

• Healthy, aged 1 to 40: vaccine alone.
• Over 40, immunocompromised, or chronic liver disease: vaccine plus human normal immunoglobulin (HNIG) 0.1 mL/kg at a separate site.
• Infants under 12 months or vaccine-contraindicated: HNIG 0.1 mL/kg alone (HAV vaccine is not licensed under 1 year).
• Outside the 14-day window: PEP is not recommended.

Twinrix must not be used for PEP: its HepA antigen dose is half the single-antigen formulations.

This is chronic hepatitis E (HEV RNA persisting beyond three months), seen almost exclusively with the zoonotic genotypes 3 and 4 in immunosuppressed hosts. The evidence-based first step is to reduce immunosuppression where the graft allows, particularly calcineurin inhibitors such as tacrolimus, because this restores the host response and clears the virus in a meaningful minority of patients. If viraemia persists, ribavirin monotherapy is the usual next step and clears most remaining cases.

A overstates interferon: it can clear chronic HEV but carries a rejection risk in organ recipients, so ribavirin is preferred. B is a category error, since nucleos(t)ide analogues target the HBV reverse transcriptase and have no activity against HEV. C is false in the immunosuppressed, where genotype 3 readily becomes chronic and can progress to cirrhosis if ignored. E is the wrong direction: more immunosuppression worsens HEV replication and persistence.

A non-responder cannot mount protective antibody quickly, so a high-risk exposure is covered with passive antibody twice. The guideline gives hepatitis B immunoglobulin now, re-immunises, and repeats the immunoglobulin at 1 month, bridging the worker through the window that a single dose would leave exposed.

A single immunoglobulin dose (A) or a booster alone (B) under-treats a proven non-responder facing an HBsAg-positive source. Starting only a vaccine course (C) is the response to a negative source, not a positive one. Dismissing the exposure (E) misjudges a needlestick from a known-positive source.

Unlike hepatitis B, hepatitis C has no post-exposure prophylaxis: there is no protective immunoglobulin and no vaccine. The exposed worker is instead monitored, with baseline and follow-up testing, and treated only if infection is established, where a short direct-acting antiviral course is curative.

Immunoglobulin (A) and a vaccine (D) do not exist for hepatitis C. Starting antivirals pre-emptively (B) is not prophylaxis and is not recommended for a mere exposure. Interferon (E) is obsolete for this indication.

The basal core promoter (BCP) double mutation A1762T + G1764A cuts pre-core mRNA transcription more than pregenomic RNA, so the patient is HBeAg-negative yet still replicates. The result is HBeAg-negative chronic hepatitis B (phase 4): HBsAg-positive, HBeAg-negative, anti-HBe positive, HBV DNA often above the 2,000 IU/mL treatment threshold, and fluctuating ALT with increased HCC risk. The classical inverse correlation between HBeAg status and viral load no longer holds.

Option A is phase 1 (HBeAg-positive, high DNA, normal ALT). B is vaccine-induced immunity. C is resolved past infection. D is an internally inconsistent HBeAg-positive but undetectable-DNA combination. Manage as phase 4: tenofovir or entecavir, usually lifelong, with six-monthly HCC surveillance; the precore G1896A mutation produces the same phenotype through a different mechanism and the two can co-exist.

Active HBV co-infection (HBsAg positive) demands a nucleos(t)ide analogue started before or with the DAA and continued for at least 12 months after DAA completion. Hepatitis C normally suppresses HBV replication; rapid DAA-driven HCV clearance lifts that suppression, and HBsAg-positive patients reactivate almost universally without cover, sometimes with severe flares. Tenofovir disoproxil fumarate, tenofovir alafenamide, or entecavir are the high-genetic- barrier agents of choice.

A baseline HBV DNA below 2,000 IU/mL (A) does not remove reactivation risk in an HBsAg-positive patient. Deferral (B) is wrong: the infections are safely co-treated. Lamivudine monotherapy (C) has an unacceptable HBV resistance rate. Vaccination (D) is futile in someone already HBsAg positive.

Direct-acting antiviral cure lowers but does not remove hepatocellular carcinoma (HCC) risk in established cirrhosis, so cirrhotic patients continue six-monthly abdominal ultrasound, with or without alpha-fetoprotein, for life. Established cirrhosis, pre-existing dysplastic foci, and durable epigenetic changes all persist after the virus is gone. Non-cirrhotic patients at SVR generally need no HCC surveillance unless specific risk factors apply.

Stopping surveillance (A) misses curable early HCC, because cure does not reverse established cirrhosis. Triphasic computed tomography (B) is for characterising a lesion found on ultrasound, not primary surveillance. Risk does not normalise within a year (D) or at any fixed 10-year point (E); it persists and is highest in the early years after cure.

Antiretroviral therapy must contain two agents active against hepatitis B virus (HBV): tenofovir plus lamivudine or emtricitabine, with a third agent such as dolutegravir (the South African first-line single-tablet regimen). Combination cover guards against HBV resistance, and the critical caveat is that the HBV-active backbone must be maintained even if the HIV regimen changes, because stopping either agent reactivates HBV with severe flares.

Adding HBV cover separately (A) risks leaving HBV unaddressed if the regimen lacks it. Lamivudine monotherapy (C) develops rapid HBV resistance and is inadequate for HIV. Abacavir (D) has no HBV activity. Delaying ART (E) is harmful, since HBV does not clear. If tenofovir is contraindicated, switch to tenofovir alafenamide or add entecavir alongside an HIV-active regimen, and monitor ALT for an immune reconstitution flare when starting at low CD4.

HAV vertical transmission is rare and not a routine clinical concern. Acute HAV in pregnancy is generally unremarkable: incidence, clinical severity and complications do not differ meaningfully from the non-pregnant adult.

Standard neonatal care applies and breastfeeding may continue. The 25 to 30% third-trimester case-fatality figure belongs to HEV, not HAV. Caesarean section, neonatal HNIG and neonatal HAV vaccine at birth are not routinely indicated for maternal HAV.

A HAV-positive food handler must be excluded from work and from patient or food contact for 7 days after the onset of jaundice. This reflects the natural history of faecal HAV shedding: peak shedding occurs in the late incubation and early symptomatic phases, falls sharply with the appearance of anti-HAV IgM, and is essentially undetectable by stool culture or PCR by about one week after jaundice appears.

Related public-health steps when an infected food handler is identified:

• PEP for co-handlers at the same establishment: post-exposure prophylaxis (PEP) is vaccine alone (single dose) for healthy adults aged 1 to 40; vaccine plus human normal immunoglobulin (HNIG) 0.1 mL/kg for those over 40, immunocompromised or with chronic liver disease, within the 14-day window.
• PEP for patrons is not routinely indicated unless onward transmission has been documented, or specific circumstances (handling ready-to-eat food after toileting without adequate hand hygiene) make patron exposure plausible.
• Outbreak notification through the Notifiable Medical Condition (NMC) system, involving the local outbreak response team.
• Premises inspection: hand-hygiene practice, kitchen cleaning, and food-storage and temperature controls.

HAV transmission from a food handler is usually mediated by uncooked or post-cooking-handled food (salad ingredients, sandwiches, garnishes, bakery items) rather than by adequately cooked meals, because cooking inactivates HAV. Risk assessment should target the specific food-preparation activities the handler performed in the seven days before symptom onset.

The 7-day post-jaundice exclusion is the operational rule. Anti-HAV IgM, transaminases and stool PCR are not used to gate return to work: they would prolong exclusion and add no public-health value.

A documented anti-HBs of 10 mIU/mL or above marks a known responder, who needs no post-exposure prophylaxis whatever the source status. Vaccine-induced immune memory protects even if the measured titre has since waned, so neither immunoglobulin nor a booster adds anything.

The immunoglobulin-containing options (C, D, E) belong to the non-responder or unvaccinated worker. A booster (B) is what you would consider for a worker of unknown response after checking the titre, not for a confirmed responder.

Guidance has shifted from risk-based to universal screening: every hepatitis B surface antigen (HBsAg) positive person should be tested at least once for hepatitis D virus (HDV), most efficiently by reflex anti-HDV testing of any HBsAg-positive sample (option A). Risk-based strategies (option B) miss a large share of infections, because risk factors are often unknown or unreported.

Option C is false: delta infection can be present with near-normal enzymes, and HDV typically suppresses hepatitis B virus (HBV) DNA, so a low HBV DNA does not exclude it. Option D confuses the requirement: HDV needs the HBsAg envelope, not hepatitis B e antigen, so patients negative for that antigen are fully susceptible. Option E would leave most cases undiagnosed; identifying HDV changes prognosis and management, and a positive anti-HDV result should be followed by an HDV RNA test to confirm active infection.

The guideline covers three overlapping groups with six-monthly alpha-fetoprotein (AFP) plus abdominal ultrasound: all cirrhotic patients at any age, all chronic HBV patients from age 30, and any patient with a family history of HCC. The age-30 inclusion of non-cirrhotic patients is a South Africa-specific feature reflecting early HCC in genotype A1, and AFP is retained alongside ultrasound because of the multifocal, rapidly doubling HCC pattern.

Option A over-includes by dropping the age-30 threshold for non-cirrhotics. B and D use an incorrect age-50 threshold and the wrong modality (CT, or AFP alone). E is wrong because surveillance is explicitly recommended. Surveillance continues lifelong, including on suppressive therapy, since viral suppression reduces but does not eliminate HCC risk.

An immune-tolerant patient (HBeAg positive, very high viral load, normal ALT) is ordinarily monitored rather than treated. The guideline shifts to treatment when the patient is over 30 with significant fibrosis or a family history of hepatocellular carcinoma or cirrhosis. At 34 this patient already meets the age condition, so a family history of hepatocellular carcinoma is the factor that pushes towards treatment.

Being under 30 (B) would keep the patient in the monitored group. HBeAg positivity (C) and a normal ALT (D) simply describe the immune-tolerant state already given. Anti-HBs positivity (E) would point away from active disease altogether.

Quantify HBV DNA at booking, then start maternal tenofovir disoproxil fumarate (TDF) at 28 to 32 weeks if HBV DNA exceeds 200,000 IU/mL. That threshold identifies women whose neonatal transmission risk remains significant despite HBIG and birth-dose vaccine, and the last-trimester benefit reduces residual transmission to under 2%. Women already on a tenofovir-containing antiretroviral regimen continue unchanged.

Starting TDF at 14 weeks (B) adds drug exposure without extra benefit, since the transmission-reduction effect comes from the third trimester. Awaiting delivery (C) leaves the residual 5 to 10% transmission from high-viraemia mothers unaddressed. Caesarean section (D) is not indicated to prevent HBV vertical transmission, and breastfeeding (E) is not contraindicated in a suppressed mother; transmission through milk is negligible.

In South African practice, immunosuppressed patients (including HIV-positive patients with reduced CD4 counts or chronic liver disease) receive the standard two-dose HAV vaccine schedule plus a third booster dose at 6 to 12 months after the first dose, to improve seroconversion.

Seroconversion in HIV-positive patients falls to between 52% and 94% compared with over 99% in immunocompetent adults, which is the rationale for the extra dose. The inactivated vaccine is safe at any CD4 count.

Anti-HAV IgM should be requested only when there is a clinical syndrome of acute hepatitis: clinical compatibility plus markedly raised transaminases. Outside this context the pre-test probability is low and the positive predictive value (PPV) of the test falls accordingly.

This is a Bayesian fact about any test:

• In a population with 1% prevalence and a test with 95% specificity, the PPV is roughly 16%: most positives are false.
• In symptomatic adults with acute icteric hepatitis (around 50% prevalence), the same test has a PPV over 95%.

The other options are wrong for specific reasons:

• HAV does not reactivate: there is no latent state.
• Recent HAV vaccination produces IgG, not detectable IgM.
• IgM does not persist from remote infection: it falls below the detection threshold within four to six months, leaving lifelong IgG as the marker.
• Cross-reactivity with anti-HEV IgM is uncommon with modern assays.

Maternal antiviral cover is the part of the perinatal pathway that targets the small group at highest transmission risk. When the HBV DNA is above 200,000 IU/mL, tenofovir disoproxil fumarate is started from 28 to 32 weeks and continued to 12 weeks postpartum, lowering the viral load before delivery so that the infant immunoprophylaxis has the best chance of working.

Treating every HBsAg-positive mother (A) is unnecessary, since below the threshold the birth-dose vaccine and immunoglobulin suffice. The 2,000 IU/mL figure in C is the chronic-hepatitis treatment threshold, not the perinatal one. Waiting until delivery (D) leaves no time to suppress the viral load, and the 36-week start in E is too late.

Both drugs are first-line, but TAF is preferred where the renal and bone toxicity of TDF is a concern: age over 60, a low estimated glomerular filtration rate, bone disease, and dialysis. The dialysis patient with reduced bone density in option E fits every part of that profile, and TAF is accessed through a Section 21 application.

A young adult with normal kidneys (A) has no reason to move off standard TDF. Pregnancy (B) favours TDF, which has the larger safety record in that setting. Paediatric use (C) is a separate licensing question, not a TDF-versus-TAF toxicity trade-off. In HIV co-infection (D) the tenofovir component is already supplied by the antiretroviral regimen.

HAV in endemic South African settings is typically acquired in early childhood, when infection is usually subclinical or mild and confers lifelong immunity. Universal childhood immunisation has historically not been judged cost-effective on these grounds: the burden of clinical disease prevented is small.

The policy is increasingly vulnerable to the epidemiological transition under way in South Africa: as sanitation improves and the age at first infection rises, the susceptible adolescent and adult population grows, and adult HAV is symptomatic and severe.

HAV vaccine is available in the private sector and recommended for defined at-risk groups: chronic liver disease, HIV-positive patients, men who have sex with men (MSM), healthcare workers, food handlers, raw-sewage workers, international travellers to endemic regions, and household, sexual and daycare contacts of acute cases.

HAV belongs to the genus Hepatovirus, family Picornaviridae. Other relevant genera in the family include Enterovirus (poliovirus, coxsackieviruses, rhinoviruses) and Aphthovirus (foot-and-mouth disease virus).

The five clinically important hepatitis viruses belong to five different families, sharing only their clinical syndrome rather than their lineage:

• HAV: Picornaviridae
• HBV: Hepadnaviridae
• HCV: Flaviviridae (genus Hepacivirus)
• HDV: Kolmioviridae (genus Deltavirus)
• HEV: Hepeviridae

The quasi-enveloped form (eHAV) is HAV wrapped in a piece of host cell membrane, released non-lytically from hepatocytes. The membrane lacks viral glycoproteins but renders the virion resistant to neutralising antibody until it is stripped in the endolysosome of the next cell.

Bile salts strip the membrane in the biliary tract: HAV in stool is naked, HAV in blood is cloaked. The cloaked blood form is the predominant viraemic form and helps explain how HAV produces a prolonged transmissible viraemia despite an active humoral response.

Passive antibody has to be in place before the virus establishes infection, so timing is tight. Prophylaxis is regarded as ineffective if given more than 7 days after a needlestick or perinatal exposure. Immunoglobulin should therefore be given as soon as possible, ideally within 24 hours, not held pending source results.

The 14-day figure in option D is the separate window for a sexual exposure, a common point of confusion. The occupational immunoglobulin dose itself is 0.06 mL/kg (about 500 IU) intramuscularly, given with the first vaccine dose at a different site.

Chronic hepatitis E occurs almost only in the immunosuppressed, typically genotype 3 in a transplant recipient. Management is stepwise: reduce immunosuppression first, which alone clears many cases, then give ribavirin (600 to 800 mg daily) if the virus persists.

Supportive care alone (A) is right for acute, self-limiting hepatitis E, not the chronic form. There is no licensed pan-genotypic direct-acting antiviral (B) or hepatitis E vaccine (D) in this setting, and interferon (C) is avoided in transplant recipients because it can precipitate graft rejection.

SVR12 is undetectable HCV RNA 12 weeks after the last dose of direct-acting antiviral therapy, and is equivalent to virological cure with a lifetime late-relapse rate well below 1%. The defining feature is persistence of suppression off therapy, not on it. SVR4 predicts SVR12 with about 99% positive predictive value. Cure does not confer sterilising immunity, so reinfection remains possible in ongoing-risk groups, and HCC surveillance continues in cirrhotic patients.

A single on-treatment undetectable result (A) is not SVR12. Anti-HCV antibody persists for life and does not serorevert (B). A ten-fold fall at week 12 (C) was the interferon-era early virological response, now irrelevant. Core antigen (E) is an RNA surrogate, not the defining cure endpoint.

HAV circulates as a single serotype worldwide. The species Hepatovirus A contains five genotypes: I, II and III infect humans (subdivided into sub-genotypes IA, IB, IIA, IIB, IIIA and IIIB), while IV and V are non-human primate strains. Despite the genetic diversity, antibodies raised against any one strain cross-neutralise all the others.

This is the basis of universal vaccine efficacy: a vaccine derived from a single strain protects against every wild-type HAV the recipient might encounter anywhere in the world.

Two consecutive QC values beyond 2 SD on the same side of the mean violate the 2-2s rule, indicating systematic error: reject the run and investigate. A consistent one-directional displacement points to a shift rather than random scatter, and the timing immediately after a lot change is the classic signal of an unrecognised lot shift.

A single 2 SD excursion (A) is only a warning; neither value reaches 3 SD (B); R-4s (D) requires opposite sides; 10-x (E) requires ten values. The action is to reject the run, re-establish the QC mean and SD for the new lot from at least 20 in-control measurements, recalibrate, and re-run affected samples.

Hepatitis A virus (HAV) is not directly cytopathic. Very high viral loads accumulate in the liver well before any biochemical or histological evidence of injury, and the ALT rise coincides with the appearance of anti-HAV immunoglobulin M (IgM) and the cellular immune response.

The injury is immune-mediated, predominantly by CD8 cytotoxic T cells and multifunctional CD4 T cells acting on infected hepatocytes. This also explains why hepatitis A is self-limiting: once the adaptive response clears infected hepatocytes, no reservoir remains.

In the SA public sector, anti-HAV IgM and anti-HAV IgG enzyme immunoassays are available at all service levels (primary, secondary and tertiary). IgM diagnoses acute infection; IgG marks past infection or vaccination.

HAV RNA reverse-transcription PCR (RT-PCR) is not routinely available at primary level and is used principally for outbreak investigation, genotyping and food or environmental samples rather than for individual patient diagnosis.

HBsAg negative, anti-HBs positive, anti-HBc total negative is the signature of vaccine-induced immunity. The recombinant vaccine contains only HBsAg, so it raises anti-HBs but cannot induce anti-HBc; natural recovery always produces both.

Susceptibility (A) is excluded by the positive anti-HBs. Past infection (B) would need anti-HBc positive. The window period (D) would need HBsAg and anti-HBc IgM positive. An escape mutant (E) would need HBsAg with anti-HBs and anti-HBc coexisting. Confirm protection with an anti-HBs titre of at least 10 mIU/mL.

South African practice specifies two weeks after the onset of jaundice, provided transaminases are below 100 U/L, as the threshold for an adult to return to work or school after acute hepatitis A.

• Transaminases should ideally normalise before return to full-time work; the 100 U/L threshold is a minimum.
• Return to sport is permitted only after both full-time work tolerance and normal transaminases. Premature return is associated with relapsing hepatitis A.

A separate 7-day post-jaundice exclusion applies to food handlers, targeting the period of infectious faecal shedding. For a food handler who is also an adult worker, both rules apply in parallel, whichever is longer.

Harvey Alter, Michael Houghton, and Charles Rice shared the 2020 prize. Alter identified non-A non-B hepatitis as a distinct bloodborne agent in transfusion recipients; Houghton’s team cloned the virus in 1989 by immunoscreening a chimpanzee-plasma complementary DNA library, identifying clone 5-1-1; Rice proved the cloned genome was infectious and built the cell-culture systems that enabled direct-acting antiviral development.

The other trios won for different agents: Montagnier and Barré-Sinoussi for HIV (2008); Blumberg for HBV and Temin for reverse transcriptase; Watson, Crick and Wilkins for the DNA double helix (1962); Karikó and Weissman for modified-mRNA technology (2023). HCV has no licensed vaccine, and Susan Solomon is not a laureate.

The same enzyme both matures the virus and disarms innate immunity: NS3/4A cleaves the four downstream non-structural polyprotein junctions, and it also cleaves the adaptors MAVS and TRIF, abolishing RIG-I and TLR3-driven type I interferon induction in the infected hepatocyte. The -previr protease inhibitors (glecaprevir, voxilaprevir, grazoprevir, and the obsolete telaprevir and boceprevir) block the active site and, as a bonus, spare MAVS and TRIF.

The structural junctions are cut by host signal peptidase, not NS3/4A, so D is wrong, and lamivudine has no HCV activity. NS3 does carry a separate helicase domain (B), but that is not the immune-evasion function, and sofosbuvir targets NS5B. NS3/4A disables rather than activates innate immunity, so C is wrong, and the -asvirs target NS5A. miR-122 is bound by the HCV RNA itself (E), the target of miravirsen, not by NS3/4A.

Under current ICTV binomial nomenclature (MSL40, 2024), the formal species name is Hepatovirus A: the genus name Hepatovirus plus a single-word epithet. “Hepatitis A virus” remains the everyday common name in clinical and laboratory practice.

The guideline anchors its treat-versus-monitor decisions to a sex-specific ALT upper limit of normal: 35 U/L in men and 25 U/L in women. These thresholds are lower than the laboratory reference ranges printed on many result slips, so a “normal” ALT on the report can still be above the guideline limit and tip a patient into a treatment band.

Option C is the AASLD figure (30 in men, 19 in women), a plausible near-miss but not the value this guideline uses. Option D inverts the sexes. The 40 U/L cut-offs in A and E reflect older generic laboratory ranges rather than the guideline.

In South Africa, viral hepatitis (including types A, B, C and E) is a Category 2 Notifiable Medical Condition (NMC). Suspected or confirmed cases require written or electronic notification to the Department of Health (usually via the NICD NMC App) within seven days of diagnosis by clinicians or testing laboratories.

Impaired responders need both a larger antigen dose and an extra dose. Dialysis and immunocompromised adults receive four doses of 40 µg at 0, 1, 2 and 6 months, then annual anti-HBs monitoring with a booster if the titre falls under 10 mIU/mL.

Option A is the standard immunocompetent adult schedule (0, 1, 6 months at the ordinary dose), which under-immunises this group. The reduced or two-dose regimens in B, C and D would leave many of these patients unprotected.

Vertical transmission from a viraemic mother runs at ~2 to 4% when the mother is HIV-negative, rising to ~10 to 25% with HIV co-infection. Transmission is mainly intrapartum, through micro-transfusion of maternal blood, with a smaller in-utero component; maternal antibody is not protective. Caesarean section does not reduce the risk, and breastfeeding is not contraindicated unless the nipples are cracked and bleeding.

The ~30% figure (A) fits HBeAg-positive HBV, not HCV, and HIV does modify the risk. Transmission is not zero without HIV (B), and there is no protective transplacental immunity. It is not 50%, and caesarean section does not lower it (C). It is well above 1% and not purely postnatal (D).

Hepatitis D is defective and can only infect people who are already HBsAg positive, because it needs the hepatitis B surface antigen to assemble. Preventing hepatitis B therefore prevents hepatitis D, so hepatitis B vaccination is the only prophylaxis.

There is no hepatitis D-specific vaccine (B) or immunoglobulin (D). Interferon (C) is a treatment for established infection, not prophylaxis, and bulevirtide (E) is an entry inhibitor used therapeutically, not for pre-exposure prevention.

Anti-HCV antibody screening identifies exposure but cannot separate current infection from cleared infection, so a reactive screen is confirmed with HCV RNA by polymerase chain reaction (PCR), or HCV core antigen where nucleic acid testing is unavailable. Many laboratories now reflex the RNA test automatically onto every antibody-positive sample, and point-of-care RNA supports same-day test and treat.

Antibody alone (A) misses the key question of active viraemia. Genotyping (C) is not a screening test; it follows confirmation and only where the regimen depends on it. The recombinant immunoblot (D) is obsolete, superseded by direct RNA. Core antigen (E) is a useful RNA surrogate but is less sensitive than antibody in early infection, so it does not replace the screen.

HAV has an incubation period of 15 to 50 days, with a mean of approximately 28 days.

Two practical implications:

• Post-exposure prophylaxis (PEP) must be given within 14 days of exposure, a short window relative to the incubation period, so PEP decisions need to be made promptly.
• A returned traveller presenting with jaundice two to six weeks after return from an endemic destination fits the HAV incubation window (and the overlapping HEV window of 15 to 60 days).

Treatment cures nearly everyone, so prioritisation is about who is harmed most by waiting. Significant fibrosis (F3 or cirrhosis) heads the priority order, followed by HIV or hepatitis B co-infection, extrahepatic disease, acute hepatitis C, transplant recipients, and people who inject drugs.

Patients with little or no fibrosis (B and C) can safely wait their turn. A person who is anti-HCV positive but HCV RNA negative (D) is not viraemic and needs no treatment at all. Declining harm reduction (E) is not a treatment-priority criterion; treatment is itself part of prevention.

Faecal shedding falls after the onset of jaundice, so exclusion is tied to that landmark: the guideline excludes a case until 2 weeks after the onset of jaundice, provided the AST and ALT are under 100 U/L.

Waiting for jaundice to resolve entirely (A) is unnecessarily long, and a fixed 7-day (C) or 6-week (E) rule ignores the jaundice landmark. Anti-HAV IgM (D) can persist for months after infectivity has passed, so it does not gauge when a case can return.

HAV severity is strongly age-dependent:

• Children under six: about 70% are asymptomatic, the silent paediatric infection that drives HAV transmission in endemic settings.
• Older children and adults: typically develop the classical icteric illness.
• Older adults: progressively more severe disease, with cholestatic, relapsing and rarely fulminant variants concentrating in this group.

This age gradient drives the age-stratified PEP algorithm: healthy 1 to 40-year-olds receive vaccine alone, while those over 40 (or with chronic liver disease) receive vaccine plus human normal immunoglobulin (HNIG).

The covalently closed circular DNA (cccDNA) mini-chromosome is the cure barrier. Formed when host enzymes repair the incoming relaxed-circular DNA, it is the template for all viral transcripts, self-replenishing through nucleocapsid recycling, untargeted by any licensed agent, and persists for the lifespan of the long-lived hepatocyte. This is why the realistic ceiling is functional cure (sustained HBsAg loss) rather than complete cure (cccDNA eradication), and why investigational tools (CRISPR/Cas9, base editors, capsid assembly modulators, siRNA plus immune modulators) are built around depleting or silencing it.

The polymerase does mutate (A), but that drives resistance, not the cure barrier. The envelope (C) is an antibody target, not a cure obstacle. Tenofovir (D) has essentially no established resistance after a decade of use. Integration (E) contributes HBsAg and HCC risk but is a replication side-product; cccDNA persistence is the principal barrier.

The guideline uses simple, widely available scores to stage fibrosis when biopsy and elastography are not to hand. An APRI (aspartate aminotransferase to platelet ratio index) above 2 indicates cirrhosis, which is itself a “treat regardless” trigger alongside decompensation, acute liver failure and impending immunosuppression.

For orientation on the elastography scale, significant fibrosis (F2) sits above roughly 7 to 8.5 kPa and cirrhosis (F4) above roughly 11 to 14 kPa. So the 6 kPa in option B is below the F2 threshold, and an APRI of 0.5 (option A) is reassuring. The isolated viral load in C and the mildly raised ALT in E are ordinary monitoring parameters, not markers of cirrhosis.

South Africa is dominated by genotype A, mainly subgenotype A1, which accounts for ~90 to 97% of isolates in rural Black populations. Its significance is a roughly four-fold higher hepatocellular carcinoma (HCC) risk in young Black men compared with non-A genotypes, with a younger onset (third to fourth decade) and HCC often arising without cirrhosis. This is why NDoH 2019 surveillance extends to non-cirrhotic chronic HBV from age 30 and retains alpha-fetoprotein alongside ultrasound. Genotype A also responds better to pegylated interferon than genotype D.

Genotype B (A) and C (B) predominate in East Asia, not South Africa. Genotype E (C) dominates West Africa. Genotype D (E) is Mediterranean and only a minor urban contributor locally.

Genotype 5 (subtype 5a) was first identified in South Africa and stays mostly confined to southern Africa, where genotypes 1 and 5 co-dominate in the general population while genotype 4 is rising with migration. In people who inject drugs the picture shifts to genotype 1a (~73%) and 3a (~15%), with genotype 5 not yet detected in that group. Pan-genotypic regimens (sofosbuvir/velpatasvir, glecaprevir/pibrentasvir) cover genotype 5 with sustained virological response above 95%.

Genotype 1a (A) is globally dominant but was not first identified in South Africa. Genotype 3a (B) drives steatosis and faster fibrosis but is global. Genotype 4 (C) is increasing locally yet originates in Egypt and central Africa. Genotype 8 (E) is the most recently described genotype, first found in a Punjabi Indian cohort.

The high-affinity entry receptor is sodium taurocholate co-transporting polypeptide (NTCP, encoded by SLC10A1), a hepatocyte bile-acid transporter engaged by the myristoylated preS1 region. Low-affinity heparan sulfate proteoglycan binding tethers the virion first, but NTCP confers the species- and tissue-specificity. Bulevirtide (Hepcludex) is a preS1-derived lipopeptide that blocks NTCP; it is licensed for chronic hepatitis delta, with a limited role in HBV monoinfection because it does not clear established cccDNA.

CD4 (A) is the HIV receptor; ACE2 (B) is SARS-CoV-2; the asialoglycoprotein receptor (C) is not the principal entry receptor and sofosbuvir is an HCV drug; heparan sulfate proteoglycan (E) mediates only initial tethering, and tenofovir targets the polymerase, not entry.

Sofosbuvir/velpatasvir for 12 weeks is a pan-genotypic first-line regimen, with sustained virological response (SVR12) above 95% across all eight genotypes, and is the standard in the South African NDoH 2019 guideline. Glecaprevir/pibrentasvir (8 weeks in treatment-naive non-cirrhotic patients) is the other first-line option, and sofosbuvir plus daclatasvir is the low-cost generic alternative.

Pegylated interferon plus ribavirin (A) is the obsolete pre-DAA standard. Telaprevir and boceprevir (C) are withdrawn first-generation protease inhibitors. The drugs in D are antiretrovirals with no HCV activity. Ribavirin monotherapy (E) is not curative and is only ever an adjunct to DAAs.

Lamivudine resistance is mediated by mutations in the YMDD motif: M204V or M204I, often stabilised by L180M. This is the prototype nucleoside-analogue resistance pattern, reaching ~70 to 80% by five years and making lamivudine unsuitable as first-line monotherapy.

Adefovir resistance (B) is N236T (D domain) and A181T/V, not M204V. Entecavir (C) needs the lamivudine backbone (M204V/I) plus an entecavir-specific mutation, so N236T alone is wrong and naive resistance is very rare. Tenofovir (D) has no clinically established resistance, and M250V is an entecavir mutation. Telbivudine (E) selects M204I (cross-resistant with lamivudine), not T184G. First-line for chronic HBV is tenofovir or entecavir, and tenofovir remains fully active against lamivudine-resistant mutants.

The 45-year-old man (E) has HBeAg-negative chronic hepatitis with HBV DNA above the 2,000 IU/mL threshold, sustained ALT elevation, and APRI 1.4 indicating significant fibrosis, so treatment is indicated. He meets two independent NDoH 2019 criteria (the HBeAg-negative pattern and fibrosis evidence); start tenofovir or entecavir.

Patient A is phase 1 (immune tolerant): high DNA but normal ALT, no fibrosis, under 30, so the immune-tolerant threshold is not met, monitor. Patient B has coexisting HBsAg and anti-HBs with undetectable DNA and no active disease, investigate rather than treat. Patients C and D have no active HBV infection (isolated anti-HBc, and vaccine-induced immunity respectively). Treatment is also indicated regardless of these thresholds for cirrhosis or APRI above 2, HIV co-infection, pregnancy with HBV DNA above 200,000 IU/mL, and planned immunosuppression.

Hepatitis E virus (HEV) is a small non-enveloped, positive-sense single-stranded RNA virus (Baltimore class IV) in the family Hepeviridae. Under current taxonomy the human virus is the species Paslahepevirus balayani in the genus Paslahepevirus. The genome is about 7.2 kilobases, capped, and carries three open reading frames: ORF1 encodes the non-structural polyprotein (methyltransferase, protease, helicase, RNA-dependent RNA polymerase), ORF2 the capsid, and ORF3 a small phosphoprotein that acts as an ion channel and is needed for virion release. In blood the particle is quasi-enveloped by host membrane, whereas in bile and faeces it is non-enveloped.

A describes a picornavirus organisation (a single polyprotein). C describes hepatitis B (Hepadnaviridae, DNA, reverse transcription). D describes hepatitis C (Flaviviridae, enveloped, single polyprotein). E describes hepatitis D (circular negative-sense RNA with a ribozyme).

Sofosbuvir is a uridine nucleotide analogue prodrug that the HCV NS5B RNA-dependent RNA polymerase incorporates into the growing RNA chain, where its modified 2’-fluoro-2’-methyl sugar terminates chain extension. Its high genetic barrier makes clinical resistance rare, and it is the backbone of most pan-genotypic regimens.

The other options misassign the target. Ganciclovir inhibits the cytomegalovirus DNA polymerase (after UL97 phosphorylation), not HIV integrase. Simeprevir is an HCV NS3/4A protease inhibitor, not a neuraminidase inhibitor. Cabotegravir is an HIV-1 integrase strand-transfer inhibitor, not an HBV reverse transcriptase inhibitor. Lenacapavir is an HIV-1 capsid inhibitor, not a SARS-CoV-2 protease inhibitor.

Now that regimens are pan-genotypic, genotype rarely changes the choice, and the decision turns on fibrosis and duration. Glecaprevir / pibrentasvir treats all genotypes in 8 weeks in a non-cirrhotic patient, the shortest option. Sofosbuvir / velpatasvir and sofosbuvir / daclatasvir are also pan-genotypic but run 12 weeks, so the 24-week figure in option A is wrong.

Interferon (D) and ribavirin monotherapy (E) belong to the pre-DAA era and have no place as first-line hepatitis C treatment. Weight-based ribavirin is added only where a regimen specifies it for cirrhotic or treatment-experienced patients.

The discriminator is the marker of recent hepatitis B infection. In acute co-infection both viruses are caught together, so IgM anti-HBc is positive; in superinfection the hepatitis B is long-standing, so IgM anti-HBc is negative. This distinction matters: co-infection usually clears both viruses (over 95%), whereas superinfection becomes chronic in 70 to 90% and drives rapid cirrhosis.

HBsAg (A), HDV RNA (B) and IgM anti-HDV (D) are positive in both scenarios, so none separates them. Anti-HBs (E) would not be present during active surface-antigenaemia.

HAV in pregnancy is generally unremarkable: the clinical course does not differ meaningfully from non-pregnant adults, and vertical transmission is rare.

HEV in pregnancy is dramatically different. HEV genotype 1 (the faecally transmitted genotype endemic in South Asia and parts of Africa) in the third trimester carries a 25 to 30% case-fatality rate driven by fulminant hepatic failure.

In any pregnant patient with acute hepatitis, HEV must be actively tested for, particularly when HAV serology is negative. HEV genotype 3 (the zoonotic genotype in high-income countries) does not carry the same pregnancy mortality.

The hepatitis D virus (HDV) genome is the smallest of any human virus: about 1.7 kilobases of circular, negative-sense, single-stranded RNA folded into an unbranched rod-like shape (option E). It contains a ribozyme that self-cleaves the multimeric products of replication, and because HDV encodes no polymerase, replication proceeds in the nucleus by host RNA polymerase II through a rolling-circle mechanism. The single protein product, the delta antigen, exists in a small (replication) and a large (assembly) form.

Option A describes hepatitis B virus (partially double-stranded circular DNA, reverse transcriptase); option B a picornavirus-like positive-sense RNA strategy (as in hepatitis A or hepatitis E); option C a segmented cytoplasmic negative-sense RNA virus such as influenza; and option D a large double-stranded DNA virus encoding its own capsid, whereas HDV borrows its envelope (HBsAg) from hepatitis B and has no capsid of its own.

HAV encodes only one viral protease, 3C (3Cpro), a cysteine protease that performs every internal cleavage of the polyprotein. This is distinctive within Picornaviridae: enteroviruses also carry a 2A protease and aphthoviruses an L protease, but HAV has neither.

Two cleavages are not performed by 3C: the C-terminal trim of VP1, and the late maturation cleavage of VP0 into VP4 and VP2 after RNA packaging. Both are performed by unknown host proteases.

Twinrix contains about half the HepA antigen dose of single-antigen HAV vaccines (720 ELU per Twinrix dose versus 1,440 ELU in the adult Havrix dose). Single-dose vaccine PEP relies on a high antigen load to drive rapid seroconversion within the 14-day window, and the half-dose does not reliably achieve this.

For routine pre-exposure vaccination against both HAV and HBV, Twinrix is fine: the full three-dose course cumulatively delivers a full HAV antigen exposure. For PEP, choose single-antigen Havrix or Vaqta.

Post-exposure prophylaxis is stratified by who mounts a reliable vaccine response. The hepatitis A vaccine (non-inferior to immunoglobulin) is used for healthy people aged 1 to 40, while immunoglobulin is reserved for those under 2, over 40, or immunocompromised. The 18-month-old in option D falls in the under-2 group, and the vaccine is in any case not licensed below 1 year.

All the other contacts are healthy adults aged 1 to 40, so each receives the vaccine within the 14-day window. Because many South African adults are already immune, screening for anti-HAV before vaccinating healthcare workers is cost-effective.

A positive antibody marks exposure, not current infection, so the pathway runs from confirming viraemia to proving cure.

a. Confirm viraemia. The antibody-positive result triggers a mandatory reflex quantitative HCV RNA. A positive RNA confirms active (viraemic) infection; a negative RNA means past or cleared infection, needing only reassurance and continued harm reduction.

b. Work up before treatment. Test for HIV and HBsAg (co-infection changes management and carries a reactivation risk), and stage fibrosis with APRI, FIB-4 or elastography.

c. Treat. Give a pan-genotypic direct-acting antiviral regimen, checking for and managing drug interactions, which matter in this population.

d. Confirm cure. Measure HCV RNA 12 weeks after treatment ends; an undetectable result is a sustained virological response, which equals cure.

Ongoing harm reduction continues throughout, and reinfection is possible, so retesting is offered if exposure continues.

The perinatal pathway is the highest-yield prevention activity in hepatitis B, built around three numbers: a viral load of 200,000 IU/mL, a gestational window of 28 to 32 weeks, and a neonatal window of 12 to 24 hours.

a. Assess the mother. Quantify the HBV DNA. Maternal antiviral treatment is indicated when the viral load is above 200,000 IU/mL, which identifies the pregnancies at highest transmission risk.

b. Maternal antiviral. Give tenofovir disoproxil fumarate from 28 to 32 weeks, continued to 12 weeks postpartum, to suppress the viral load before delivery.

c. Immunise the neonate. Every baby of an HBsAg-positive mother receives the monovalent hepatitis B birth dose plus hepatitis B immunoglobulin (HBIG), at different sites, within 12 to 24 hours of birth. (HBIG is recommended for the highest-risk neonates but is not currently available in the public sector.)

d. Complete and confirm. Give the routine hexavalent infant series at 6, 10 and 14 weeks, then check HBsAg and anti-HBs at 9 to 18 months; an anti-HBs of 10 mIU/mL or above confirms protection.

Caesarean section is not indicated, and breastfeeding is safe once the mother is virally suppressed.

TDF can cause a proximal renal tubulopathy, so the annual review is built around renal safety.

• Serum creatinine (or estimated glomerular filtration rate): tracks falling renal function, which also prompts a dose reduction or a switch to tenofovir alafenamide.
• Serum phosphate: hypophosphataemia is an early marker of the proximal tubular injury TDF causes.
• Urine protein: tubular proteinuria signals the same nephrotoxicity before creatinine rises.
• Rationale: together these detect TDF-associated nephrotoxicity early, allowing a change of agent before lasting renal or bone harm.

Acute liver failure is the point at which acute hepatitis becomes an emergency needing tertiary care and transplant assessment. The defining features are:

• Hepatic encephalopathy: altered mental state signalling loss of hepatic function.
• Coagulopathy with an INR over 1.5: synthetic failure, the key laboratory marker.
• Deepening jaundice: rising bilirubin marking severe hepatocellular injury.

Any of these in a patient with acute hepatitis warrants referral to a centre with transplant access.

A complete answer gives an ordered cascade from screening serology to confirmatory viral load, and notes who to test and how to assess disease stage.

Who to test. Current guidance favours screening every hepatitis B surface antigen (HBsAg) positive person for hepatitis D virus (HDV) at least once, rather than restricting testing to recognised risk groups, since risk-based screening misses a substantial fraction of cases. Many laboratories achieve this by reflex testing: an anti-HDV assay is run automatically on any HBsAg-positive sample.

The serological and molecular cascade.

1. Screen with total anti-HDV antibody. A positive result indicates exposure but does not by itself distinguish past from current infection, because antibody persists after clearance.
2. Confirm active infection with HDV RNA. A quantitative reverse transcription polymerase chain reaction (RT-PCR) on serum confirms ongoing replication and provides a baseline viral load for monitoring. Standardisation against the World Health Organization international unit allows comparison across assays. HDV RNA is the reference marker of active infection.
3. Genotype where available, since genotype influences prognosis (genotype 1 is global; genotype 3 in the Amazon is more severe).

Staging the liver disease. Active hepatitis D requires assessment of the underlying liver: alanine aminotransferase, a full liver profile and synthetic function (albumin, international normalised ratio), platelet count, and non-invasive fibrosis assessment by transient elastography or the APRI or FIB-4 scores. Because chronic hepatitis D progresses rapidly, established cirrhosis must be sought, and cirrhotic patients enter six-monthly hepatocellular carcinoma surveillance with ultrasound and alpha-fetoprotein. HBV markers (hepatitis B e antigen, HBV DNA) are quantified in parallel, since HDV typically suppresses HBV replication.

A complete answer establishes that hepatitis E is more than a liver disease, names the principal neurological and renal syndromes, and notes the genotype association.

Neurological disease

Neurological injury is the best-characterised extrahepatic manifestation of hepatitis E virus (HEV), reported in a notable proportion of symptomatic genotype 3 infections in case series from Europe. The two most recognised syndromes are:

• Guillain-Barre syndrome: an acute immune-mediated demyelinating polyradiculoneuropathy causing ascending weakness, temporally linked to acute HEV infection.
• Neuralgic amyotrophy (Parsonage-Turner syndrome): severe shoulder-girdle pain followed by patchy upper-limb weakness, often bilateral in HEV-associated cases.

Other reported neurological associations include encephalitis, myelitis, meningoradiculitis and peripheral neuropathy. HEV RNA can sometimes be detected in cerebrospinal fluid, suggesting both direct and immune-mediated mechanisms.

Renal and haematological disease

Renal involvement includes acute kidney injury and glomerulonephritis, including membranoproliferative glomerulonephritis with cryoglobulinaemia. Haematological associations include thrombocytopenia and aplastic anaemia, and acute pancreatitis is also described.

Practical relevance

The breadth of these associations means HEV should be considered in a patient presenting with one of these neurological syndromes and deranged liver enzymes, even without prominent hepatitic symptoms, particularly in regions where genotype 3 circulates.

A complete answer contrasts the tempo of disease and the principal complications of chronic hepatitis D against hepatitis B alone, and gives the reason for the difference.

Tempo of progression. Chronic hepatitis D is the most rapidly progressive form of chronic viral hepatitis. Cirrhosis develops in a large proportion of patients within 5 to 10 years of chronic infection, considerably faster than in hepatitis B virus (HBV) monoinfection, where progression to cirrhosis typically unfolds over decades. Once cirrhosis is established, hepatitis D carries a higher annual risk of hepatic decompensation and an increased risk of hepatocellular carcinoma compared with HBV alone.

Why hepatitis D is more severe. The acceleration reflects the added burden of a second replicating virus driving immune-mediated injury on top of the HBV background, producing more intense necroinflammation. The route of acquisition shapes outcome: superinfection of an established HBV carrier chronifies in the great majority and is the usual path to progressive disease, whereas simultaneous co-infection mostly resolves like an acute hepatitis B and only occasionally becomes chronic.

The HBV interaction. Hepatitis D characteristically suppresses HBV replication, so HBV DNA is often low or undetectable even as liver disease advances. This can mislead, because a patient who looks like an inactive HBV carrier on HBV markers may in fact have aggressive ongoing delta hepatitis. Outcomes improve only with sustained suppression of HDV RNA or, ideally, loss of hepatitis B surface antigen, which removes the envelope the delta virus requires.

A complete answer states precisely which step of the life cycle hepatitis D virus (HDV) cannot perform alone, and distinguishes what it borrows from hepatitis B virus (HBV) from what it provides itself.

Why HDV is defective. HDV is a satellite virus: it can replicate its genome inside a hepatocyte without help, but it cannot make its own envelope and therefore cannot assemble or transmit infectious particles without a helper. That helper is HBV. Infection with HDV occurs only in people who are also hepatitis B surface antigen (HBsAg) positive.

What HDV provides itself. HDV supplies its own genome (a small circular negative-sense RNA), its ribozyme for processing replication products, and its single protein, the delta antigen. The small delta antigen supports genome replication; the large delta antigen, generated by host RNA editing and modified by farnesylation, drives packaging. Replication itself uses host RNA polymerase II, not an HBV enzyme, which is why nucleos(t)ide analogues that suppress HBV polymerase have no direct effect on HDV.

What it borrows from HBV. The single essential contribution from HBV is the surface (envelope) protein, HBsAg. HDV wraps its ribonucleoprotein in the HBsAg envelope to form an infectious virion, and uses the same preS1-mediated binding to the sodium taurocholate co-transporting polypeptide (NTCP) receptor that HBV uses to enter hepatocytes. This dependence has two consequences: HDV can only be acquired alongside or after HBV, and any therapy or vaccine that removes HBsAg (or prevents HBV infection) also defeats HDV.

A complete answer states why hepatitis D is hard to treat, describes the established and newer agents with their mechanisms, and defines a realistic endpoint.

The therapeutic problem. Chronic hepatitis D is the most rapidly progressive viral hepatitis, yet the delta virus encodes no enzyme of its own to target: it is replicated by host RNA polymerase II. Nucleos(t)ide analogues that suppress hepatitis B virus (HBV) polymerase therefore do nothing directly to hepatitis D virus (HDV). The durable goal of therapy is loss of hepatitis B surface antigen (HBsAg), which removes the envelope HDV depends on, but this is rarely achieved.

Established therapy. Pegylated interferon-alpha was for decades the only option. A 48-week course achieves an undetectable HDV RNA in roughly a quarter of patients, but relapse is common, the drug is poorly tolerated, and it is contraindicated in decompensated cirrhosis. It remains an option in compensated disease.

Newer and emerging therapy.

• Bulevirtide is a first-in-class entry inhibitor: a myristoylated lipopeptide derived from the HBV preS1 sequence that binds and blocks the sodium taurocholate co-transporting polypeptide (NTCP), the shared HBV and HDV hepatocyte receptor, preventing infection of new cells. Given as a daily subcutaneous injection, it is licensed in Europe for chronic hepatitis D, reducing HDV RNA and normalising transaminases in a substantial proportion of patients (bile-acid elevation is an expected on-treatment effect of NTCP blockade).
• Lonafarnib, a farnesyl-transferase inhibitor, blocks the prenylation step the large delta antigen needs for assembly, and is under trial evaluation, including in combination with interferon.

Realistic goals. Outside the rare achievement of HBsAg loss, therapy aims to suppress HDV RNA, normalise transaminases, and slow fibrosis progression. Access is a major constraint: bulevirtide is licensed mainly in Europe and is not yet widely available in high-burden African and Asian settings.