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Hepatitis A

The hepatitis A virus (HAV) causes infection of the liver and is a major cause of illness worldwide.

HAV is a small RNA virus, a member of the Hepatovirus genus of the picornavirus family, which can survive in food and water and is relatively resistant to detergents. The virus was first identified in human faeces in 1973 and later identified in blood. HAV is primarily a human infection but has been also identified in nonhuman primates. Hepatitis A causes acute hepatitis only and does not lead to chronic liver disease.

Hepatitis A is a vaccine preventable disease.

Epidemiology
Hepatitis A virus replicates in hepatocytes and is secreted via bile into the intestine. Faeces contains large amounts of virus, thus the primary mode of transmission is faecal-oral in contrast to the parenteral or blood-borne spread of hepatitis B and C.

In Australia, most transmission of hepatitis A is from person to person, often among family members in the same household, between sexual partners (especially from oral-anal contact) and among people who have occupational exposure to the virus, such as child-care centre workers or those employed in residential institutions.

Clinical Features
The incubation period (time between exposure to the virus and the development of signs and symptoms) varies between 15 and 40 days and averages 28 days. Viral shedding in faeces reaches a peak just before clinical symptoms become apparent and thus patients are most infectious prior to the onset of symptoms.