Bit · Micro
Hepatitis A vs B vs C vs D vs E
Five viruses that all damage the liver but split sharply on transmission, genome, chronicity, and pregnancy risk. The pivot is the route plus whether you can go chronic.
Mechanism
The vowels (A and E) are fecal-oral and do not go chronic in immunocompetent hosts. The consonants (B, C, D) are blood/sexual and can go chronic.
- HAV — RNA, picornavirus. Acute hepatitis, often subclinical in kids. Vaccine available.
- HBV — partially double-stranded DNA, hepadnavirus. Has its own DNA polymerase with reverse-transcriptase activity. Vaccine available (HBsAg subunit). Serology is the high-yield bit — HBsAg, anti-HBs, HBcAb (IgM vs IgG), HBeAg.
- HCV — RNA, flavivirus. ~50–80% become chronic. No vaccine. Direct-acting antivirals now curative.
- HDV — defective RNA virus; requires HBV's HBsAg coat to replicate. Co-infection or superinfection with HBV.
- HEV — RNA, hepevirus. Like HAV (fecal-oral, acute). But dangerous in pregnancy — fulminant hepatic failure with high mortality.
Differentiator Table
| HAV | HBV | HCV | HDV | HEV | |
| Genome | RNA (+ssRNA) | DNA (partial dsDNA) | RNA (+ssRNA) | RNA (-ssRNA, circular) | RNA (+ssRNA) |
| Family | Picornavirus | Hepadnavirus | Flavivirus | Deltavirus | Hepevirus |
| Transmission | Fecal-oral | Blood, sexual, perinatal | Blood (IVDU, transfusion pre-1992) | Requires HBV — same routes | Fecal-oral (often contaminated water) |
| Chronicity | No | 5–10% adults, >90% perinatal | 50–80% | Yes (worse with HBV) | No (except immunocompromised) |
| Pregnancy risk | Standard acute | Vertical transmission to neonate | Lower vertical risk | As HBV | Fulminant hepatic failure (~20% mortality) |
| Vaccine | Yes | Yes (HBsAg) | No | Indirect via HBV vaccine | Limited (available in some countries) |
| HCC risk | No | Yes | Yes | Yes (with HBV) | No |
| Treatment | Supportive | Entecavir, tenofovir | DAAs (e.g. sofosbuvir + ledipasvir) — curative | Treat underlying HBV | Supportive (ribavirin in chronic) |
The Pivot
Two questions usually settle it:
- How was it transmitted? Fecal-oral → HAV or HEV. Blood/sexual → HBV, HCV, HDV.
- Acute self-limited or chronic? Acute, kids, no chronic carriage → HAV. Acute, pregnant woman, fulminant → HEV. Chronic carrier with risk of cirrhosis/HCC → HBV or HCV. Acute-on-chronic worsening of a known HBV → consider HDV superinfection.
For HBV, learn the serology pattern (HBsAg, anti-HBs, IgM/IgG anti-HBc, HBeAg) cold — NBME asks it constantly.
NBME-Style Stem
A 26-year-old woman in her third trimester of pregnancy presents with jaundice, malaise, and acute liver failure. She returned from rural South Asia two months ago, where she drank well water. Hepatitis A IgM is negative. Hepatitis B surface antigen is negative. Hepatitis C antibody is negative. Which of the following is the most likely cause?
Concept Anchor
The vowels (A, E) come in through the mouth and leave the body without staying; the consonants (B, C, D) get in through blood or sex and can move in for life — with HBV and HCV driving cirrhosis and HCC, and HDV only existing as HBV's parasite.