Gastrointestinal & Hepatic · Topic 9 of 26

Viral Hepatitis

Hepatic · viral hepatitis A, B, C and E

Viral Hepatitis

Read the hepatitis B panel marker by marker, confirm hepatitis C antibody with RNA, and cure hepatitis C with an 8–12-week pangenotypic regimen.

Key numbers

Pangenotypic DAA for 8–12 weeks8 wk G/P · 12 wk S/V

Cure = undetectable HCV RNA at 12 weeksSVR at ≥ 12 wk

01 · Defined byHBsAg plus IgM anti-HBc = acute HBV

HBsAg means current HBV infection; IgM anti-HBc marks acute infection (and can be the only marker in the window after HBsAg clears); HBsAg with IgG anti-HBc persisting ≥ 6 months means chronic HBV.

02 · Defined byHCV antibody, then reflex HCV RNA

Test for hepatitis C with anti-HCV and reflex HCV RNA: antibody-positive with detectable RNA is current infection; antibody-positive with undetectable RNA is cleared or cured infection.

03 · GivePangenotypic DAA for 8–12 weeks

Treat essentially every patient with chronic HCV with a pangenotypic direct-acting antiviral: glecaprevir/pibrentasvir for 8 weeks or sofosbuvir/velpatasvir for 12 weeks (treatment-naive, no cirrhosis); genotyping is not needed first.

Causes & risk factors

Why it happens

Chronicity: HCV 65–85%, adult HBV 1–12%Acute HCV becomes chronic in about 65–85% of patients, whereas acute HBV becomes chronic in only about 1–12% of immunocompetent adults (far more often when acquired in infancy); HAV and usually HEV do not.

Hepatitis E is dangerous in pregnancyHepatitis E (fecal-oral, often travel or contaminated water) is diagnosed by IgM anti-HEV or HEV RNA and is usually self-limited, but pregnant patients have a higher risk of acute liver failure and death.

Presentation

What you'll see

HBeAg signals high replication and infectivityHBeAg indicates active viral replication and high infectivity; anti-HBe suggests lower infectivity. e-antigen markers guide prognosis and therapy more than diagnosis.

Diagnosis & monitoring

Work-up

Anti-HBs alone = vaccinated; plus anti-HBc = recovered must knowAnti-HBs alone (HBsAg and anti-HBc negative) means vaccine immunity; anti-HBs with anti-HBc means recovered past infection; all three negative means susceptible — vaccinate.

IgM anti-HAV = acute hepatitis A must knowAcute hepatitis A is diagnosed by IgM anti-HAV; HAV spreads fecal-orally, is treated supportively and never becomes chronic — total anti-HAV with negative IgM means past infection or vaccination.

Cure = undetectable HCV RNA at 12 weeksCheck quantitative HCV RNA and liver panel 12 or more weeks after therapy; an undetectable RNA (sustained virologic response) is a cure, with > 99% staying RNA-negative.

Management

Orders

Check HBV status before HCV treatmentTest HBsAg, anti-HBc and anti-HBs before starting HCV antivirals: HBV reactivation causing liver failure and death has occurred during or after DAA therapy, so monitor and consider HBV antivirals in those with HBV.

Entecavir or tenofovir for chronic HBVFirst-line chronic HBV therapy is entecavir, TDF or TAF; treat immune-active disease (ALT ≥ 2× ULN with HBV DNA ≥ 20,000 IU/mL if HBeAg-positive, ≥ 2,000 if negative) and all cirrhosis regardless of viral load.

Acute HBV: supportive unless severe or failingAcute HBV is managed supportively (> 95% of adults recover); give entecavir or tenofovir only for acute liver failure or a severe protracted course — bilirubin > 3 mg/dL, INR > 1.5, encephalopathy or ascites.

HBV prophylaxis before immunosuppression or rituximabHBsAg-positive patients get entecavir or tenofovir before chemotherapy or immunosuppression; HBsAg-negative, anti-HBc-positive patients can be monitored, except with rituximab (anti-CD20) or stem cell transplant, which need prophylaxis.

Treat acute HCV without waitingTreat acute HCV at diagnosis with the same DAA regimens as chronic HCV, without waiting for spontaneous clearance; test HCV RNA first after exposure within 6 months or when immunocompromised (antibody may be negative).

Red flags & don'ts

Avoid harm

No protease inhibitors in decompensated cirrhosis avoidDo not use HCV protease inhibitors ("-previr", e.g., glecaprevir) in decompensated cirrhosis; treat with a hepatologist, ideally at a transplant center. Prior treatment, cirrhosis, HBsAg positivity and pregnancy exclude simplified treatment.

The rules

Know these

Screen all adults once for HBV and HCVCDC recommends screening every adult 18 or older at least once for HCV (and in every pregnancy) and at least once for HBV with the triple panel — HBsAg, anti-HBs and total anti-HBc.

Acute or chronic hepatitis B?

Commonly confused

HBsAg	Positive
Anti-HBc class	IgM
Anti-HBs	Negative (appears with recovery)
Antiviral treatment	Only for liver failure or a severe, protracted course

More detail

Reference

Show 8 reference facts

Isolated anti-HBc may mean occult HBV, an HBsAg mutant, resolved infection with waned anti-HBs (counsel on reactivation risk) or a false positive (vaccinate).

Chronic genotype 3 hepatitis E occurs in immunocompromised patients, especially solid-organ transplant recipients; reduce immunosuppression first, and ribavirin may be used.

If confirmed HBV infection is severe, test anti-HDV for hepatitis D co-infection or superinfection.

Screen for hepatocellular carcinoma every 6 months with ultrasound (± alpha-fetoprotein) in HBV with cirrhosis or other high-risk features (family history of HCC, HDV co-infection, older age) and in HCV with advanced fibrosis or cirrhosis.

Pregnant patients with HBV DNA > 200,000 IU/mL at any point receive TDF or TAF from gestational week 28 (TDF has the longer safety record) to prevent mother-to-child transmission.

After sexual or percutaneous exposure to HBsAg-positive blood, give hepatitis B immune globulin 0.06 mL/kg IM plus vaccine; a vaccinated person with anti-HBs < 10 mIU/mL gets a booster.

HAV fecal shedding usually ends within days of symptom onset; acute liver failure is rare and more likely with preexisting liver disease.

AASLD–IDSA 2026 widens HBV treatment: suggest antivirals in the immune-tolerant phase (HBeAg-positive, HBV DNA > 10⁷ IU/mL, normal ALT) when age > 40 or ≥ F2 fibrosis, and shared decisions in indeterminate phases.

Pearl

Surface antigen means infection, surface antibody means immunity, core antibody means the virus was met — IgM core means it was met recently.

Sources · Merck Manual Professional — Hepatitis B, Acute (serology table) · Merck Manual Professional — Hepatitis B, Chronic (cites the 2026 AASLD/IDSA chronic hepatitis B guideline) · Terrault NA et al. Update on prevention, diagnosis, and treatment of chronic hepatitis B: AASLD 2018 hepatitis B guidance. Hepatology 2018;67:1560–1599 · CDC — Clinical Testing and Diagnosis for Hepatitis B (triple-panel screening, interpretation) · Merck Manual Professional — Hepatitis C, Chronic · Merck Manual Professional — Hepatitis C, Acute · AASLD/IDSA HCV Guidance — Simplified HCV Treatment for Treatment-Naive Adults Without Cirrhosis · CDC — Clinical Screening and Diagnosis for Hepatitis C · Merck Manual Professional — Hepatitis A · Merck Manual Professional — Hepatitis E · Ghany MG et al. AASLD–IDSA Practice Guideline on treatment of chronic hepatitis B. Hepatology 2026;83(4):974–997 · Starter sheet built from the verified AGACNP fact map (facts reviewed 2026-10-15).