Acute Hepatitis A

Acute hepatitis A is self-limited liver infection caused by hepatitis A virus (HAV), a non-enveloped RNA picornavirus.

• Transmission is faecal-oral through contaminated water, shellfish and raw produce, person to person contact, and sexual (oral-anal) contact; outbreaks occur where sanitation is poor.
• Incubation is 15 to 50 days (average 28).
• In endemic settings most infection occurs in early childhood and is asymptomatic, which produces lifelong immunity; adults without prior exposure have severe disease.

Children under 6 years are usually anicteric; over 70 percent of adults are symptomatic.

• Prodrome: fever, malaise, anorexia, nausea, vomiting, abdominal discomfort, then dark urine, pale stool, jaundice and pruritus for 2 to 6 weeks.
• Tender hepatomegaly; splenomegaly and cervical lymphadenopathy in some.
• Differential diagnosis: hepatitis B, C, D and E, Epstein-Barr virus, cytomegalovirus, leptospirosis, malaria, yellow fever, typhoid, drug-induced liver injury, autoimmune hepatitis, biliary obstruction.
• Complications: cholestatic hepatitis (jaundice for over 12 weeks), relapsing hepatitis (up to 10 percent), acute liver failure (0.3 percent; higher over age 50 years and with chronic liver disease), autoimmune hepatitis trigger, Guillain-Barre syndrome, pancreatitis, acute kidney injury, aplastic anaemia.

Anti-HAV IgM positive confirms acute infection (persists 3 to 6 months); anti-HAV IgG indicates past infection or vaccination.

• ALT and AST usually above 1000 IU/L, raised bilirubin and alkaline phosphatase; INR and albumin for synthetic function.
• Full blood count, glucose, creatinine; rule out hepatitis B (HBsAg, IgM anti-HBc), C (anti-HCV) and E.
• Ultrasound if pain or cholestasis.

Supportive

• Outpatient care for most; hydration, small frequent meals, rest as tolerated, no alcohol, avoid hepatotoxic drugs, paracetamol limited to 2 g daily.
• Admit for INR above 1.5, vomiting with dehydration, encephalopathy, age over 50 years, comorbid liver disease, pregnancy or immunosuppression.
• Pruritus: cholestyramine 4 g up to three times daily; severe cholestasis, prednisolone 40 mg daily for 7 days then taper over 3 weeks.

Pharmacological

• No specific antiviral therapy.
• Acute liver failure: intensive care, N-acetylcysteine (150 mg/kg over 1 hour, then 50 mg/kg over 4 hours, then 100 mg/kg over 16 hours), lactulose 30 mL every 6 to 8 hours, glucose monitoring, vitamin K 10 mg IV, transplant referral.

Prevention and contacts:

• Inactivated vaccine, 2 doses 6 to 12 months apart (adult dose 1440 ELISA units, children 720 units), for travellers, outbreak contacts, men who have sex with men, people with chronic liver disease, and in endemic outbreaks.
• Post-exposure prophylaxis within 14 days for household and sexual contacts: vaccine (for ages 1 to 40 years) or human normal immunoglobulin 0.02 mL/kg IM (for infants under 1 year, adults over 40 years, immunocompromised or liver disease, with vaccine).
• Hygiene: handwashing, safe water, sanitation; exclude food handlers for 7 days after jaundice onset.

Special groups: pregnancy (supportive; risk of preterm labour), elderly (higher mortality), chronic liver disease (vaccinate).

Red flags: encephalopathy, bleeding, hypoglycaemia, INR above 1.5, persistent vomiting, renal failure.

Follow-up: ALT and bilirubin weekly until falling then monthly until normal; relapse expected within 6 months in a minority; lifelong immunity after recovery.