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Hepatitis A Associated with Consumption of Frozen Strawberries -- Michigan, March 1997

In March 1997, a total of 153 cases of hepatitis A were reported in Calhoun County, Michigan (1990 population: 136,000); 151 case-patients have been students or staff of schools in four different school districts. Investigation by public health officials has not implicated a single event, foodhandler, or contaminated water as a source for the outbreak. However, most case-patients ate lunch in schools, and preliminary analysis of both a case-control and cohort study conducted in two different school districts established a strong association between illness and consumption of food items containing frozen strawberries. This report presents the preliminary findings of the ongoing outbreak investigation.

The strawberries associated with illness were reportedly from Mexico; a company in southern California processed, packed, and froze the strawberries in 30-pound containers for commercial use and then distributed the strawberries to U.S. Department of Agriculture (USDA)-sponsored school lunch programs. In addition, multiple packing sizes were distributed to other commercial customers. Thirteen lots of frozen strawberries, processed on three dates in April and May 1996 and shipped to Michigan in early December, were available for use in school lunch programs in Calhoun County during the potential exposure periods for the case-patients. The investigation has not determined whether transmission was limited to a portion of the 13 lots or the source of the contamination.

The Food and Drug Administration is working with CDC and USDA to determine whether any frozen strawberries or products made from the strawberries are still in distribution and need to be recalled. USDA has notified state agencies to place an immediate hold on all unused product and to contact school districts to hold all unused product distributed already. States other than Michigan that received the implicated lots for the school lunch program are Arizona, California, Georgia (from a distributor in Florida), Iowa, and Tennessee.

CDC notified the health departments in the six states that received these lots for their programs and recommended that they determine whether the frozen strawberries were served. Postexposure prophylaxis with immune globulin (IG) should be offered only to persons who consumed frozen strawberries from the suspected lots through school lunch programs within 14 days of their exposure. Because of the limited supply of IG nationwide, these criteria for administration of IG should be strictly applied. Health-care providers and public health departments should be alert to any increase in the incidence of hepatitis A and should investigate cases rapidly. Hepatitis A cases suspected to be associated with the consumption of frozen strawberries should be reported promptly to local or state health departments, and CDC's Hepatitis Branch, Division of Viral and Rickettsial Diseases, National Center for Infectious Diseases should be notified (telephone {404} 639-2709).

Information regarding IG for postexposure prophylaxis should be obtained from state health departments. Information about the prevention of hepatitis A can be obtained from the recommendations of the Advisory Committee on Immunization Practices (1).

Reported by: Calhoun County Dept of Public Health, Battle Creek; Michigan Dept of Community Health; Michigan Dept of Agriculture; Michigan Dept of Education. Food and Drug Br, California Dept of Health Svcs. Food Distribution Div, Food and Consumer Svc; Fruit and Vegetable Div, Agricultural Marketing Svc, US Dept of Agriculture. Detroit District, Detroit, Michigan; Los Angeles District, Los Angeles, California; Food and Drug Administration. Hepatitis Br, Div of Viral and Rickettsial Diseases, National Center for Infectious Diseases, CDC.


  1. CDC. Prevention of hepatitis A through active or passive immunization: recommendations of the Advisory Committee on Immunization Practices (ACIP). MMWR 1996;45(no. RR-15).

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