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Appendix G
PROSPECTS FOR IMMUNIZING AGAINST HEPATITIS A VIRUS

Disease Description

Hepatitis A virus (HAV) infection is a more prevalent but somewhat less serious disease than that caused by the hepatitis B virus. It has a worldwide distribution and often occurs in epidemic clusters. HAV is spread primarily by the fecal-oral route; outbreaks often may be traced to contaminated food or community water supplies. Secondary epidemic waves may follow a known outbreak when close personal contacts of the original victims develop the disease (McCollum, 1982). Some researchers suspect that HAV also may be spread by the respiratory route, but there is no conclusive evidence to support this theory.

The age distribution of HAV infection depends on the level of sanitation. In developing countries, infection and acquisition of antibodies occur early, when the disease is usually mild. As sanitation improves and the incidence of disease declines, infection may be delayed to an age at which symptoms are far more severe.

In young children, HAV illness is often anicteric and may be entirely subclinical. When symptoms do occur, they may include jaundice, fever, malaise, fatigue, headache, anorexia, nausea, vomiting, and abdominal pain. Adults with HAV illness may be sick enough to require hospitalization. The disease has no known sequelae and is rarely fatal. Apart from the transient viremia that occurs during early HAV infections, there has been no identification of viremic carriers (Mosley, 1975). Risk factors for hepatitis A infections include involvement in day care, homosexuality, personal contact with infected individuals, and foreign travel.

The advice and assistance of M.J.Alter, J.L.Dienstag, and D.P. Francis in the preparation of this appendix are gratefully acknowledged. The committee assumes full responsibility for any judgments or assumptions.



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