Emerging Infectious Diseases Outbreak of Salmonella enteritidis Associated with Nationally Distributed Ice Cream Products -- Minnesota, South Dakota, and Wisconsin, 1994

From September 19 through October 10, 1994, a total of 80 confirmed cases of Salmonella enteritidis (SE) infection were reported to the Minnesota Department of Health (MDH); in comparison, 96 cases were reported statewide during all of 1993. Cases were characterized by diarrhea, abdominal cramps, and fever. Recent increases in SE cases also were reported from South Dakota (14 cases during September 6-October 7, compared with 20 cases during all of 1993) and Wisconsin (48 cases during September 6- October 7, compared with 187 during all of 1993). This report summarizes preliminary findings from the outbreak investigation.

On October 5 and 6, to assess potential risk factors for infection, the MDH conducted a case-control study of 15 cases and 15 age- and neighborhood-matched controls. A case was defined as culture-confirmed SE in a person with onset of illness during September. Eleven case-patients (73%) and two controls (13%) reported consumption of Schwan's ice cream within 5 days of illness onset for case-patients and a similar period for controls (odds ratio=10.0; 95% confidence interval=1.4-434.0).

On October 7 and 9, the MDH issued press releases informing the public of this problem and advising persons who had been ill since September 1 and who had consumed Schwan's ice cream to contact the health department. During October 8-11, a total of 2014 persons who had consumed suspected products and had been ill with diarrhea contacted the MDH by telephone. Samples of ice cream from households of ill persons grew SE.

Ill persons reported eating all types and flavors of ice cream products produced at the Schwan's plant in Marshall, Minnesota, including ice cream, sherbet, frozen yogurt, and ice cream sandwiches and cones; these products had production dates in August and September. The implicated products are distributed nationwide, primarily by direct delivery to homes, and are sold only under the Schwan's label. Investigations to examine the extent and causes of the outbreak are under way.

On October 7, the company voluntarily stopped distribution and production at the Marshall plant pending further findings from these investigations. Reported by: Acute Disease Epidemiology Section, Minnesota Dept of Health. South Dakota Dept of Health. Wisconsin Dept of Health and Social Svcs. Center for Food Safety and Applied Nutrition, Food and Drug Administration. Foodborne and Diarrheal Diseases Br, Div of Bacterial and Mycotic Diseases, National Center for Infectious Diseases, CDC.

Editorial Note

Editorial Note: Gastroenteritis caused by Salmonella is characterized by abdominal cramps and diarrhea, vomiting, fever, and headache. Antimicrobial therapy is not indicated in uncomplicated gastroenteritis, which typically resolves within 1 week. Persons at increased risk for infection or more severe disease include infants; the elderly; persons with achlorhydria; those receiving immunosuppressive therapy; persons who may have received antimicrobials for another illness; and those persons with sickle-cell anemia, cancer, or acquired immunodeficiency syndrome (1). Complications include meningitis, septicemia, Reiter syndrome, and death (1).

Salmonella sp. are second only to Campylobacter as a cause of bacterial diarrheal illness in the United States, causing an estimated 2 million illnesses annually (2). Among the more than 2000 Salmonella serotypes, SE has ranked first or second in frequency of isolation from humans since 1988 and accounted for 21% of reported isolates in 1993. Each year, an average of 55 outbreaks of SE infections are reported to CDC; approximately 11% of patients are hospitalized, and 0.3% die (3).

Preliminary findings from this outbreak indicate that the number of persons exposed to contaminated products may be substantial. Approximately 400,000 gallons of the implicated products are produced weekly and are distributed throughout the contiguous United States. Previous investigations have established the potential for large-scale outbreaks of foodborne salmonellosis; for example, in 1985, pasteurized milk produced at one dairy plant caused up to 197,000 Salmonella infections (4).

Consumers should discard or return any Schwan's ice cream products. Persons who have become ill since September 1 with diarrhea and who have consumed Schwan's ice cream products are urged to contact their state health departments.

References

1. Pavia AT, Tauxe RV. Salmonellosis: nontyphoidal. In: Evans AS, Brachman PS, eds. Bacterial infections in humans: epidemiology and control. 2nd ed. New York: Plenum Medical Book Company, 1991:573-

3. Helmick CG, Griffin PM, Addiss DG, Tauxe RV, Juranek DD. Infectious diarrheas. In: Everheart JE, ed. Digestive diseases in the United States: epidemiology and impact. Washington, DC: US Department of Health and Human Services, Public Health Service, National Institutes of Health, National Institute of Diabetes and Digestive and Kidney Diseases, 1994:85-123; DHHS publication no. (NIH)94-1447.

4. CDC. Outbreaks of Salmonella enteritidis gastroenteritis -- California, 1993. MMWR 1993; 42:793-7.

5. Ryan CA, Nickels MK, Hargrett-Bean NT, et al. Massive outbreak of antimicrobial-resistant salmonellosis traced to pasteurized milk. JAMA 1987;258:3269-74.

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