|
Center for Food Safety & Applied Nutrition Foodborne Pathogenic Microorganisms and Natural Toxins Handbook |
|
|
1. Name of the Organism: Hepatitis A Virus |
Hepatitis A virus (HAV) is classified with the enterovirus group of the Picornaviridae family. HAV has a single molecule of RNA surrounded by a small (27 nm diameter) protein capsid and a buoyant density in CsCl of 1.33 g/ml. Many other picornaviruses cause human disease, including polioviruses, coxsackieviruses, echoviruses, and rhinoviruses (cold viruses). |
| 2. Name of Acute Disease: | The term hepatitis A (HA) or type A viral hepatitis has replaced all previous designations: infectious hepatitis, epidemic hepatitis, epidemic jaundice, catarrhal jaundice, infectious icterus, Botkins disease, and MS-1 hepatitis. |
| 3. Nature of Disease: | Hepatitis A is usually a mild illness characterized by sudden onset of fever, malaise, nausea, anorexia, and abdominal discomfort, followed in several days by jaundice. The infectious dose is unknown but presumably is 10-100 virus particles. |
| 4. Diagnosis of Human Illness: | Hepatitis A is diagnosed by finding IgM-class anti-HAV in serum collected during the acute or early convalescent phase of disease. Commercial kits are available. |
| 5. Associated Foods: | HAV is excreted in feces of infected people and can produce clinical disease when susceptible individuals consume contaminated water or foods. Cold cuts and sandwiches, fruits and fruit juices, milk and milk products, vegetables, salads, shellfish, and iced drinks are commonly implicated in outbreaks. Water, shellfish, and salads are the most frequent sources. Contamination of foods by infected workers in food processing plants and restaurants is common. |
| 6. Frequency of Disease: |
Hepatitis A has a worldwide distribution occurring in both
epidemic and sporadic fashions. About 22,700 cases of
hepatitis A representing 38% of all hepatitis cases (5-year
average from all routes of transmission) are reported annually
in the U.S. In 1988 an estimated 7.3% cases were foodborne or
waterborne. HAV is primarilly transmitted by person-to-person
contact through fecal contamination, but common-source
epidemics from contaminated food and water also occur. Poor
sanitation and crowding facilitate transmission. Outbreaks of
HA are common in institutions, crowded house projects, and
prisons and in military forces in adverse situations. In
developing countries, the incidence of disease in adults is
relatively low because of exposure to the virus in childhood.
Most individuals 18 and older demonstrate an immunity that
provides lifelong protection against reinfection. In the
U.S., the percentage of adults with immunity increases with
age (10% for those 18-19 years of age to 65% for those over
50). The increased number of susceptible individuals allows
common source epidemics to evolve rapidly.
|
| 7. Usual Course of Disease: | The incubation period for hepatitis A, which varies from 10 to 50 days (mean 30 days), is dependent upon the number of infectious particles consumed. Infection with very few particles results in longer incubation periods. The period of communicability extends from early in the incubation period to about a week after the development of jaundice. The greatest danger of spreading the disease to others occurs during the middle of the incubation period, well before the first presentation of symptoms. Many infections with HAV do not result in clinical disease, especially in children. When disease does occur, it is usually mild and recovery is complete in 1-2 weeks. Occasionaly, the symptoms are severe and convalescence can take several months. Patients suffer from feeling chronically tired during convalescence, and their inability to work can cause financial loss. Less than 0.4% of the reported cases in the U.S. are fatal. These rare deaths usually occur in the elderly. |
| 8. Target Population: | All people who ingest the virus and are immunologically unprotected are susceptible to infection. Disease however, is more common in adults than in children. |
| 9. Analysis of Foods: | The virus has not been isolated from any food associated with an outbreak. Because of the long incubation period, the suspected food is often no longer available for analysis. No satisfactory method is presently available for routine analysis of food, but sensitive molecular methods used to detect HAV in water and clinical specimens, should prove useful to detect virus in foods. Among those, the PCR amplification method seems particularly promising. |
| 10. Selected Outbreaks: |
Hepatitis A is endemic throughout much of the world. Major
national epidemics occurred in 1954, 1961 and 1971. Although
no major epidemic occurred in the 1980s, the incidence of
hepatitis A in the U.S. increased 58% from 1983 to 1989.
Foods have been implicated in over 30 outbreaks since 1983.
The most recent ones and the suspected contaminated foods
include:
A summary of foodborne Hepatitis A outbreaks in Missouri, Wisconsin, and Alaska is found in MMWR 42(27):1993 Jul 16. MMWR 39(14):1990 Apr 13 summarizes foodborne outbreaks of Hepatitis A in Alaska, Florida, North Carolina, Washington. |
| For more information on recent outbreaks see the Morbidity and Mortality Weekly Reports from CDC. |
mow@cfsan.fda.gov
January 1992 with periodic updates
