Hepatitis A virus - Replication, Epidemiology, Transmission

Replication of Hepatitis A virus

Hepatovirus A replicates in the cytoplasm of the infected cell. Although the primary site of replication for the Hepatitis A virus (HAV) is the hepatocyte, the factor that determines the tissue tropism has not been elucidated.

The replication and virus undergo the following steps:

• Attachment and entry

• Uncoating and translation/genome replication

• Assembly and exit

  (The host cell receptor has not been identified)

After the attachment and entry of the Hepatitis A virus into the host cell, the virus loses the capsid and the uncoated RNA induces the host cell to produce polyprotein without shutting off the protein synthesis of the cell.

Genome replication takes place simultaneously. The viral RNA is then encapsidated into the virus. These viruses are released by exocytosis.

Epidemiology of Hepatitis A virus

Hepatitis A virus has a worldwide distribution. The infection is more common in the developing countries of Asia, Africa, and South America with poor sanitation. In developing countries Hepatitis A is endemic and more than 90% of the adult population is immune.

Between the 1980s and 1990s in Nepal, nearly all adolescents were reported to be immune by the age of 15. Humans are the reservoir of the Hepatitis A virus. Humans infected with the Hepatitis A virus are an important source of infection.

Transmission of Hepatitis A virus

Hepatitis A virus infection is transmitted primarily by the fecal-oral route (contaminated food/water). Consumption of food such as shellfish collected from sewage-contaminated water also transmits the virus.

High concentrations of the Hepatitis A virus are shed in the stools of patients 3-10 days prior to the onset of illness till 1-2 weeks after jaundice. Transmission via blood/blood products is rare as the level of viremia in Hepatitis A virus is low and chronic infection does not occur

Risk groups include:

• Those traveling in countries where the infection is endemic

• People from lower socio-economic groups (poor hygiene)

• Occupationally exposed groups (Eg: healthcare workers, sewage workers)

• Male homosexuals

• Those which chronic liver disease