Transmission of Hepatitis A infection is mainly through the faecal-oral route with the risk of person-to-person transmission being highest among household or sexual contacts of cases. Spread may also occur from ingestion of contaminated food or water. The incubation period is on average 28 days, with the period of infectivity ranging from 1-2 weeks before the onset of jaundice to 1 week after. Faecal shedding may be prolonged in children and immunosuppressed people.

Infection is often mild and self-limiting and can be asymptomatic in most children below the age of 6 years. HAV infection may be more severe in the immunosuppressed, those with chronic liver disease or chronic Hepatitis B or C infection and in the elderly. Acute liver failure is also rarely associated with HAV infection.