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Epidemiologic Notes and Reports Outbreak of Yersinia enterocolitica -- Washington State

In December 1981 and January 1982, an outbreak of predominantly gastroenteritis caused by Yersinia enterocolitica occurred among 87 persons in Washington state. The illness was associated with the ingestion of a locally produced brand of tofu, an oriental soybean curd, packed in untreated spring water. It was sold primarily in western Washington with limited distribution in Alaska, Idaho, and Oregon. Y. enterocolitica was isolated from the tofu, the processing plant's water supply, and several sites within the plant.

In mid-January 1982, the Seattle-King County Health Department received reports from two hospital laboratories of 12 positive stool cultures of Y. enterocolitica associated with gastrointestinal illness; during the previous year, 10 Y. enterocolitica isolates were reported in the entire county. Increased surveillance by Seattle-King County and the Washington State Department of Social and Health Services over several months identified additional cases, for a total of 87. A case was defined as anyone who was culture-positive and/or who had had contact with a case and had fever in conjunction with diarrhea or abdominal cramps.

Of the 87 cases, 56 were culture-positive; 38 patients had enteritis, six had only extra-intestinal infections, four had both extra-intestinal infections and enteritis, and eight were asymptomatic carriers. The 10 cases of extra-intestinal infection included patients with wound ulcers (two), inguinal lymphadenopathy (two, one with a perineal ulcer), pneumonia (two), labial infection (one), arthritis (one), septicemia (one), and pharyngitis (one). Nine (16.1%) of the 56 culture-positive patients were 1 year of age, 12 (21.4%) were 1 to 4 years old, 7 (12.5%) were 5 to 18 years old, and 28 (50.0%) were

18 years old. Among 38 culture-positive cases with enteritis, who tended to have more severe illness and on whom more complete information was available, the following were reported: fever (91%), abdominal pain (81%), diarrhea (76%), nausea (54%), vomiting (39%), bloody stools (27%), joint pain (42%), and skin rash (43%). Symptoms lasted from 1 day to 4 weeks (mean 10 days). Two patients, however, were ill for over 2 months. Seventeen patients were hospitalized for from 2 to 11 days (average 9.7 days); two of those hospitalized had appendectomies and one, a partial colectomy. One patient was also culture-positive for Salmonella typhimurium and one for rotavirus, as well as for Y. enterocolitica.

A neighborhood case-control study of 11 ill persons and 11 controls revealed an association between Y. enterocolitica infection and tofu consumption (p 0.01). Questions regarding animal contacts, water sources, raw milk consumption, travel, and day-care settings, as well as extensive food histories, did not identify any other common sources. Further investigation revealed that 70 (80.5%) of the 87 persons interviewed had consumed the same brand of tofu within the 2 weeks before onset of symptoms. For five culture-positive persons who had consumed only one meal of tofu, the incubation period averaged 6.6 days (range 4-11 days).

The tofu plant in King County is located on a rural island in Puget Sound. The plant water supply, which originates from a spring approximately 0.5 mile from the plant, is shared by four residences and an apple-cider plant. No illness was reported among consumers of the cider. Inspection of the tofu plant on January 20, 1982, disclosed unsanitary conditions, including poor personal hygiene, use of an outdoor privy, and unsanitary equipment. Samples of tofu and the plant water supply were positive for Y. enterocolitica, as were stool specimens collected from two of 12 employees; both employees were asymptomatic.

A voluntary recall of the product was instituted from January 21 to January 25. Further sampling and laboratory analysis of the tofu demonstrated high fecal-coliform counts. Production was resumed after a water-purification system was installed. Laboratory results of plasmid analysis, determination of enterotoxin production, and serotyping are pending. Reported by C Nolan, MD, N Harris, DVM, Seattle-King County Health Dept, J Ballard, MS, J Allard, PhD, J Kobayashi, MD, State Epidemiologist, Washington State Dept of Social and Health Svcs.

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