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Hepatitis A virus (HAV) is a picornavirus that is most commonly transmitted by fecaloral route. It has a relatively short incubation period of 3–4 weeks after which jaundice starts suddenly. It is unique in that it does not cause chronic disease or fatal disease.
Hepatitis A virus shows following morphological features:
· It is a typical enterovirus in the family Picornaviridae.
· It is a small, nonenveloped virus measuring 27 nm in diameter (Fig. 66-1).
· It has a single-stranded positive-sense RNA genome. The HAV was originally designated as enterovirus, but it is recognized as a prototype of Hepatovirus. The naked capsid is more stable than other picornaviruses to acid and other treatment.
Hepatitis A virus replicates in the cytoplasm of the infected cell. It has a replicative cycle similar to that of other picornaviruses. Briefly, it combines specifically with a receptor expressed on liver cells and few other cells. However, unlike other picornavi-ruses, it is not cytolytic and is released by exocytosis.
There is only one serotype in HAV. The virus does not show any antigenic relationship with hepatitis B or other hepatitis viruses.
Hepatitis A virus is highly resistant to environmental factors. It is stable at 60°C for 1 hour, 56°C for 30 minutes, and 4°C for weeks. It is stable to acidic pH, at pH 1. It is resistant to inactivation by lipid solvents, such as ether and chloroform, to action of detergents, and to drying.
The virus is inactivated by formalin (0.35%) at 37°C during a period of 24 hours and by treatment with peracetic acid (2%) for 4 hours and beta-propiolactone (0.25%) for 1 hour. It is also inac-tivated by exposure to ultraviolet radiation (2 mW/cm2/minute). The virus is inactivated by routine chlorine treatment of drink-ing water.
Hepatitis A is the only virus that can be grown in human and simian cell culture. However, it is difficult to grow routinely from feces of infected patients.
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