Hepatitis A virus (HAV) is a significant cause of infectious hepatitis and a major cause of enterically transmitted infectious hepatitis. Yearly there are about 1.5 million clinical cases of HAV infection but it is estimated that the actual rate of infection is probably as much as ten times higher. Endemic levels of HAV are related to hygienic and sanitary conditions with high-income regions having very low endemic HAV levels and low-income countries having high levels of endemicity. HAV is a nonenveloped icosahedral virion about 27 nanometers in diameter. Virions consist of single-stranded, plus sense RNA about 7,500 nucleotides long. There is a poly(A) tract on the 3’ end, within a protein capsid shell consisting of four structural proteins, designated VP1-4. Various primary and continuous primate cells will support culture adapted HAV growth. Cell lines derived from African green monkey kidney (AGMK) cells such as (BS-C-1, Vero, and BGMK), fetal rhesus kidney (FRhK4) or human hepatoma (PCL/PRF/5) tissue have been useful for studying replication and for propagating high viral titers. Many wild-type strains, however, have not been adapted to cell culture despite intensive efforts, and successful isolation from clinical specimens often requires several weeks of blind passaging. Natural infection usually occurs 3 to 4 weeks following ingestion of virus from material contaminated with human feces containing HAV. The progression of events from ingestion of HAV to replication in the hepatocyte has not been completely resolved. During incubation, viremia occurs concurrently with fecal shedding of HAV due to release of viruses via bile. There is no specific treatment for acute viral hepatitis with therapy designed to be supportive and maintaining adequate nutritional balance. Although the disease is usually mild in children under 10, those who become clinically ill are more prone to develop fulminant hepatic failure compared with those who develop clinical HAV infection between the ages of 10 to 14 years. At older than 40 years, the severity of the liver disease intensifies. HAV is on of the most common causes of infectious jaundice in the world today with routine recurrent epidemics.