The reasoning: comparative epidemiology
| Feature | HAV | HBV | HCV | HDV | HEV |
|---|---|---|---|---|---|
| Genome / family | RNA, picornavirus | DNA, hepadnavirus | RNA, flavivirus | Defective RNA (needs HBsAg) | RNA, hepevirus |
| Transmission | Faeco‑oral | Perinatal, blood, sexual, horizontal in childhood | Blood (unsafe injections, transfusion, PWID), less sexual/perinatal | With HBV (co‑ or super‑infection) | Faeco‑oral (waterborne); zoonotic genotypes 3/4 (pork) |
| Incubation | 15–50 days (≈ 28) | 30–180 days (≈ 75) | 14–180 days | — | 15–60 days (≈ 40) |
| Chronicity | No | 90% if infected at birth, 25–50% at 1–5 years, < 5% adults | 55–85% | Common (super‑infection) | Rare (immunocompromised) |
| Complications | Fulminant (rare, more in adults) | Cirrhosis, HCC | Cirrhosis, HCC | Severe, rapidly progressive | Fulminant hepatic failure in pregnancy (3rd trimester), CFR up to 20–25% |
| Prevention | Sanitation; vaccine (not in UIP) | Vaccine (birth dose + pentavalent), safe blood/injections, HBIG | No vaccine; safe injections, blood safety, harm reduction | HBV vaccination | Safe water and sanitation |
| Treatment | Supportive | Tenofovir/entecavir (selected) | DAAs (sofosbuvir + velpatasvir/daclatasvir, 12–24 weeks; SVR > 95%) | — | Supportive |