Hepatitis A

HAV, originally classified as Enterovirus type 72, is now considered to be the prototype of Hepatovirus genus in the Picornaviridae family. HAV is a non enveloped virus with a genome composed of positive-sense ssRNA, measuring 27nm in diameter. Thereis only one serotype. It is destroyed by boiling for 5 min and by treatment with chlorine.

HAV causes hepatitis A which has been called infectious hepatitis in the past. The disease occurs in sporadic or epidemic forms.

Pathogenesis

The host range for this virus is limited to humans and a few other primates. The virus is transmitted mainly by faeco-oralroute usually through ingestion of contaminated fooa and water. It affects children and young adults. Increased risk of transmission is due to decreased sanitary hygienic factors.

Clinical features

The incubation period is 2-6 weeks. Asymptomatic and subclinical infections are common in children. Viral hepatitis may be preceded by generalized gastrointestinal symptoms and fever. Nausea, vomiting, and anorexia are common symptoms. Many cases are wothout jaundice. Hepatitis A infection is usually mild, self limited and does not progress to chronic hepatitis.

Laboratory diagnosis

1 Marked elevation of liver transaminase and bilirubin.
2Detection of anti-HAV IgM (by RIA or ELISA) is diagnostic of acute phase.
3Detection of anti-HAV IgG during convalescnece. It indicates immunity and may persist for decades.
4Detection of HAV particles in stools or blood by RIA,PCR, genetic probes, or electron microscope.

Prevention and control

1Proper hand washing, chlorination or boiling of drinking water.
2 Careful disposal of sewage and avoiding contamination of fod and water.
3 An intactivated vaccine (Havrix) can be given intramuscularly (IM) as two doses above 2 years of age who live in endemic countries.
4HAV immune globulin for post exposure prophylaxis to prevent disease in the immunodeficient.
5Proper cooking.