Hepatitis questions are a USMLE classic because they’re deceptively simple on the surface (“Which virus causes chronic hepatitis?”) but quickly turn into layered vignettes with serologies, transmission clues, and complications. If you can mentally sort A–E by route, chronicity, special associations, and key labs/serologies, you’ll crush a whole category of Micro + Medicine in one go.
The Big-Picture Framework (Your Step 1 Mental Map)
Think of hepatitis viruses along three axes:
-
Transmission
- Fecal–oral: HAV, HEV
- Blood/sex/perinatal: HBV, HCV, HDV
-
Chronic infection?
- No chronic: HAV
- Usually no chronic (but can be severe): HEV (notably severe in pregnancy)
- Chronic possible: HBV, HCV, HDV (HDV only with HBV)
-
Cancer risk
- High: HBV, HCV → hepatocellular carcinoma (HCC)
- No: HAV (and HEV classically doesn’t, but can cause severe acute disease)
First Aid cross-ref: Microbiology → Viruses → Hepatitis viruses; plus Immunology (serologies), Pathology (HCC), and GI (acute vs chronic hepatitis patterns).
Quick Comparison Table (High-Yield)
| Virus | Genome/Envelope | Transmission | Incubation | Chronic? | Key complications | Vaccine? |
|---|---|---|---|---|---|---|
| HAV | +ssRNA, non-enveloped (picornavirus) | Fecal–oral (travel, daycare, outbreaks) | ~2–6 wks | No | Fulminant hepatitis rare; relapsing hepatitis can occur | Yes (inactivated) |
| HBV | Partially dsDNA, enveloped (hepadnavirus), reverse transcriptase | Blood, sex, perinatal | ~1–4 mo | Yes | Polyarteritis nodosa, membranous nephropathy, HCC | Yes (recombinant HBsAg) |
| HCV | +ssRNA, enveloped (flavivirus) | Blood (IVDU), transfusion (historic), needle sticks | ~2–6 mo | Yes (common) | Mixed cryoglobulinemia, MPGN, porphyria cutanea tarda, HCC | No |
| HDV | -ssRNA, enveloped, defective | Requires HBV (HBsAg) | variable | Yes | Severe hepatitis, fulminant risk (esp coinfection/superinfection) | Preventable via HBV vaccine |
| HEV | +ssRNA, non-enveloped (hepevirus) | Fecal–oral (contaminated water) | ~2–8 wks | Usually no (exceptions in immunosuppressed) | Fulminant hepatitis in pregnancy | No (not routinely in US) |
Pathophysiology: What’s Actually Damaging the Liver?
A Step 1 pearl: hepatitis viruses are not primarily “cytopathic.” Much of the liver injury comes from immune-mediated inflammation.
Acute hepatitis (general)
- Viral infection of hepatocytes triggers CD8+ T-cell response
- Leads to hepatocyte apoptosis/necrosis
- Lab pattern: AST/ALT elevation (often ALT > AST) ± bilirubin
Chronic hepatitis (HBV/HCV/HDV)
- Persistent infection → ongoing immune activation → fibrosis → cirrhosis
- Cirrhosis increases risk for:
- Portal HTN (ascites, varices, splenomegaly)
- Synthetic dysfunction (↑INR, low albumin)
- HCC (especially HBV/HCV)
First Aid cross-ref: Pathology of chronic hepatitis → bridging fibrosis → cirrhosis → HCC.
Clinical Presentation: How They Show Up in Vignettes
Acute viral hepatitis (common pattern)
- Prodrome: fatigue, malaise, anorexia, nausea, low-grade fever
- Then: jaundice, dark urine, RUQ discomfort, hepatomegaly
- Labs: very high ALT/AST (often hundreds to thousands), bilirubin elevated
Chronic hepatitis clues
- Many are asymptomatic until complications
- May see: fatigue, mild RUQ discomfort, extrahepatic features (esp HCV)
- Labs: persistent transaminase elevation (often fluctuating)
Hepatitis A (HAV)
Definition & virology
- Picornavirus, +ssRNA, non-enveloped
- Acid-stable → survives GI tract
Transmission & epidemiology
- Fecal–oral
- Risk settings: travel, outbreaks from contaminated food/water, daycare, homelessness/crowded living, MSM (recognized risk), close contacts
Clinical
- Acute symptomatic hepatitis more common in adults than kids
- No chronic infection
- Can have relapsing course (symptoms recur weeks later)
Diagnosis
- Anti-HAV IgM = acute infection
- Anti-HAV IgG = prior infection or vaccination (immunity)
Treatment & prevention
- Supportive care
- Vaccination (inactivated virus)
- Post-exposure prophylaxis: vaccine ± immune globulin depending on patient factors (Step often focuses on concept rather than exact algorithm)
HY associations
- Non-enveloped viruses resist detergents; “fecal-oral, non-enveloped” theme
- Outbreak vignette: restaurant exposure + abrupt jaundice + IgM positivity
First Aid tie-in: “HAV—picornavirus, fecal-oral, no chronicity.”
Hepatitis B (HBV)
Definition & virology
- Hepadnavirus
- Partially double-stranded DNA
- Enveloped
- Uses reverse transcriptase (a classic board favorite)
Transmission
- Blood, sexual, perinatal
- High-yield settings: needlestick, unprotected sex, IVDU, infant of infected mother
Clinical course
- Can be acute or chronic
- Chronicity risk is highest when infected at birth
- Neonates: high chronic risk
- Adults: most clear infection
Key extrahepatic manifestations (immune complex–mediated)
- Polyarteritis nodosa
- Membranous nephropathy
- Serum sickness–like prodrome sometimes (arthralgias, rash)
Mechanism pearl: circulating immune complexes (HBsAg-containing) deposit in vessels/kidneys.
Diagnosis: HBV serology made usable
Core rules
- HBsAg = current infection (acute or chronic)
- Anti-HBs = immunity (recovered or vaccinated)
- Anti-HBc = exposure to actual virus (not from vaccine)
- IgM anti-HBc = acute infection (or “window period” marker)
- IgG anti-HBc = prior or chronic infection
The “window period”
- HBsAg has fallen, anti-HBs not yet detectable
- Only marker: IgM anti-HBc (often with HBeAg/anti-HBe evolving)
Infectivity marker
- HBeAg correlates with high viral replication and infectivity
- Anti-HBe suggests lower infectivity (but mutant strains exist)
Treatment (Step-level)
- Acute: supportive
- Chronic: antivirals such as tenofovir, entecavir (common current first-line); interferon in select cases
Prevention
- HBV vaccine (recombinant HBsAg)
- Also prevents HDV (because HDV requires HBsAg)
HY associations
- HCC risk even without cirrhosis can occur (HBV DNA integration is a concept often tested)
- Perinatal transmission vignette: HBsAg+ mother → newborn prophylaxis (vaccine + HBIG is the classic concept)
First Aid tie-in: HBV serology chart + “DNA virus with reverse transcriptase.”
Hepatitis C (HCV)
Definition & virology
- Flavivirus
- +ssRNA, enveloped
- High genetic variability → immune escape (why no vaccine)
Transmission
- Blood exposure most high yield (IVDU, needle sticks)
- Sexual transmission is less efficient than HBV but still possible
Clinical course
- High rate of chronic infection
- Chronic infection can smolder → cirrhosis → HCC
- Many patients are asymptomatic for years
Extrahepatic manifestations (very testable)
- Mixed cryoglobulinemia
- Palpable purpura, arthralgias, weakness; can cause neuropathy
- Membranoproliferative glomerulonephritis (MPGN)
- Porphyria cutanea tarda
- Blistering photosensitivity, hyperpigmentation
- Also associated with lichen planus (sometimes tested)
Diagnosis
- Screening: anti-HCV antibodies
- Confirmation/active infection: HCV RNA (PCR)
- Assess chronic disease: viral load, genotype (less emphasized now clinically but still appears), fibrosis staging
Treatment
- Direct-acting antivirals (DAAs) (high cure rates)
- Step doesn’t require memorizing every combo, but know: curable, prevents progression, reduces transmission
HY associations
- Vignette: history of IVDU + chronic mild transaminitis + cryoglobulinemia symptoms
- Unlike HBV, no vaccine due to antigenic variability
First Aid tie-in: “HCV → chronic, HCC, mixed cryoglobulinemia/MPGN, porphyria cutanea tarda.”
Hepatitis D (HDV)
Definition & virology
- Defective virus: requires HBsAg to assemble
- -ssRNA, enveloped
How it infects: coinfection vs superinfection
- Coinfection: HBV + HDV acquired at the same time
- Can be severe acute hepatitis, but chronic infection less common than superinfection
- Superinfection: HDV infects someone who already has chronic HBV
- More severe, higher risk of fulminant hepatitis and chronic progression
Diagnosis
- Evidence of HBV infection plus:
- Anti-HDV or HDV RNA
- Worsening hepatitis in a known HBV patient is a classic clue
Treatment & prevention
- Prevention is key: HBV vaccination prevents HDV
- Treatment options are limited; interferon-based approaches historically used (Step emphasis: prevention via HBV vaccine)
HY associations
- Think: “Delta depends on B.”
- Superinfection = the “worse” one.
First Aid tie-in: HDV requires HBsAg; coinfection vs superinfection severity.
Hepatitis E (HEV)
Definition & virology
- Hepevirus
- +ssRNA, non-enveloped
Transmission
- Fecal–oral, especially contaminated water
- More common in areas with poor sanitation; travel-associated cases show up in vignettes
Clinical
- Typically acute hepatitis
- High-yield red flag: fulminant hepatitis in pregnant patients (especially in the 3rd trimester in classic teaching)
Diagnosis & treatment
- Often clinical/epidemiologic; serology/PCR exist
- Treatment: supportive (severe cases require hospitalization)
HY associations
- Pregnant patient + jaundice after travel/outbreak + acute liver failure signs → think HEV.
First Aid tie-in: “HEV—fecal-oral, high mortality in pregnant women.”
Serology & Diagnosis: Rapid Recognition Patterns
Pattern recognition bullets
- Acute HAV: anti-HAV IgM
- Past HAV or vaccinated: anti-HAV IgG
- Acute HBV: HBsAg+, IgM anti-HBc+ (often HBeAg+ early)
- Window period HBV: IgM anti-HBc+ with HBsAg- and anti-HBs-
- Chronic HBV: HBsAg+ for >6 months, IgG anti-HBc+, anti-HBs negative
- Vaccinated HBV: anti-HBs+ only (no anti-HBc)
- HCV active: HCV RNA+ (antibody may indicate exposure; RNA confirms active infection)
- HDV: HBV markers + HDV RNA/anti-HDV
- HEV: travel/water exposure + acute hepatitis (serology if tested)
Complications You’re Expected to Link (Step-Style)
Hepatocellular carcinoma (HCC)
- Strongly associated with chronic HBV and HCV
- Vignette clues:
- Cirrhosis + weight loss + RUQ pain
- Elevated AFP
- Imaging shows liver mass
- Mechanisms (conceptual)
- HBV: chronic inflammation + integration (oncogenic contribution)
- HCV: chronic inflammation (not known for integration)
Immune complex diseases
- HBV: PAN, membranous nephropathy
- HCV: mixed cryoglobulinemia, MPGN
Treatment & Prevention: What Step 1/2 Expects
| Virus | Main management | Key prevention |
|---|---|---|
| HAV | Supportive | Vaccine; sanitation; post-exposure prophylaxis concept |
| HBV | Acute supportive; chronic antivirals (e.g., tenofovir/entecavir) | Vaccine; safe sex/needles; perinatal prophylaxis concept |
| HCV | DAAs (curative) | Harm reduction; blood safety; no vaccine |
| HDV | Limited options; manage as severe HBV-related hepatitis | HBV vaccine prevents HDV |
| HEV | Supportive; hospitalize if severe | Clean water; travel precautions |
High-Yield “Classic Vignettes” (Rapid Fire)
- Daycare worker with abrupt jaundice after outbreak → HAV (IgM anti-HAV).
- Newborn of HBsAg+ mother → prevent chronic infection with HBV vaccine + HBIG (concept).
- IVDU with fatigue, arthralgias, palpable purpura + kidney disease → HCV with cryoglobulinemia/MPGN.
- Chronic HBV patient suddenly worsens (fulminant picture) → suspect HDV superinfection.
- Pregnant traveler develops acute liver failure → HEV.
First Aid Cross-Reference Checklist (Use This While You Review)
- Microbiology (Viruses): HAV/HBV/HCV/HDV/HEV basic properties (RNA/DNA, enveloped, transmission)
- Immunology/Serology: HBV markers (HBsAg, anti-HBs, anti-HBc IgM/IgG, HBeAg)
- Pathology (Liver): acute vs chronic hepatitis histology; cirrhosis; HCC; AFP
- Renal: membranous nephropathy (HBV), MPGN (HCV)
- Rheum/Vascular: PAN (HBV), cryoglobulinemia (HCV)
- OB: HEV severity in pregnancy; HBV perinatal transmission prevention concept
Final High-Yield Takeaways (If You Only Memorize 8 Things)
- Fecal–oral: HAV, HEV (both non-enveloped).
- Blood/sex/perinatal: HBV, HCV, HDV.
- HAV: no chronic, diagnose with IgM anti-HAV.
- HBV: DNA virus with reverse transcriptase; HBsAg = current infection.
- HBV window period: IgM anti-HBc is the key marker.
- HCV: most likely to become chronic; major extrahepatic disease (cryoglobulinemia, MPGN, PCT).
- HDV requires HBV (HBsAg); superinfection is worse.
- HEV is dangerous in pregnancy (fulminant hepatitis association).