Hepatitis A is an acute viral infection of the liver that is transmitted predominantly by the fecal-oral route. The disease is asymptomatic in 70% of children less than 6 years old and symptomatic in70% of older children and adults. Symptoms, which include fever, anorexia, nausea, abdominal discomfort, dark urine, and jaundice, begin an average of 28-30 days after exposure (range, 15-50 days) and usually resolve within 2 to 4 weeks. The rare fatalities (<1/1,000 cases) usually are due to acute liver failure. The infection does not produce chronic liver disease or chronic infection, and infection confers lifelong immunity. Hepatitis A cannot be distinguished from other types of viral hepatitis by symptoms; diagnosis is by detection of IgM antibody in serum.
Hepatitis A is the most common form of acute viral hepatitis in the United States, and one of the 10 most commonly reported infectious diseases. An estimated 33,000 clinical cases and 61,000 infections occur annually. While mortality is low, morbidity is relatively high: approximately 11% of cases are hospitalized, and an ill adult loses an average of 12 to 27 days of work. In Florida, an average of 654 cases have been reported annually from 2000 to 2004, with the highest rates in adults 25 to 39 years of age and children 5-9 years of age.
The virus is shed in stool. Peak shedding and peak infectivity, occur two weeks before the onset of jaundice or elevated liver enzymes and decline rapidly after symptom onset; most persons probably are noninfectious within a week after jaundice appears. Infection is acquired primarily by person-to-person contact, including sexual contact, or by ingestion of contaminated food or water. The most frequently reported source of infection (22%-26%) is either household or sexual contact with a case. In Florida, males who have sex with males have become an increasingly important risk group for hepatitis A. The proportion of reported hepatitis A cases occurring in males 20-49 years of age rose from 61.4% in 1995 to 77.2% in 2001; within that age group, the ratio of males to females increased from 1.6 to 1 in 1995 to 3.4 to 1 in 2001. In 2004, the proportion of reported hepatitis A cases occurring among males was 59.6% and the male to female ratio was 1.5.
Young children also play a key role in transmission because they are usually asymptomatic, have poorer hygiene, and may shed the virus for longer periods than adults. Restaurant associated outbreaks, although relatively uncommon, can be responsible for large numbers of cases. The state's largest hepatitis A outbreak occurred in 2001 among methamphetamine users in a large central Florida county. Transmission by transfusion is very rare because of the relatively short viremic phase.
Prevention of hepatitis A is based on proper hand washing, prophylaxis of close contacts to a case, and vaccination of high risk groups. Careful hand washing, with particular attention to fingernails and fingertips, should be done after using the toilet, changing a diaper, or handling an animal, and before eating or preparing food. Prophylaxis with immune globulin is recommended for household and sexual contacts of cases; for classroom contacts of children in day care centers; for all staff and attendees of day care centers that care for children in diapers; and for other food handlers in a facility where a case occurs in a food handler. Prophylaxis should be given as soon as possible after exposure (defined as the last contact with the case during the time of peak infectivity); it is ineffective if given more than two weeks after exposure. Vaccination is recommended for travelers to certain foreign countries, for children of migrant farm workers, for males who have sex with males, and for certain other high risk groups (1,2, 3).
Prevention of Hepatitis A Through Active or Passive Immunization: Recommendations of the Advisory Committee on Immunization Practices (ACIP)
http://www.cdc.gov/mmwr/preview/mmwrhtml/rr4812a1.htm, Vol 48, No RR12;1 10/01/1999
1. Centers for Disease Control and Prevention. 1998 guidelines for treatment of sexually transmitted disease. MMWR 1997;47 (RR-1):98-100.
2. Centers for Disease Control and Prevention. Prevention of hepatitis A through active or passive immunization. MMWR 1996;45 (RR-15).
3. Koff RS. Hepatitis A. Lancet 1998;241:1643-9.
4. Noskin GA. Prevention, diagnosis, and management of viral hepatitis: a guide for primary care physicians. Arch Fam Med 1995;4:923-34.
5. American Academy of Pediatrics. Prevention of hepatitis A infections. Pediatrics 1996;98:1207-15
6. American Academy of Pediatrics. Hepatitis A. In: Peter G, ed. 1997 Red Book: report of the Committee on Infectious Diseases. 24th ed. Elk Grove Village, Il: American Academy of Pediatrics; 1997:237-46.
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