In the period August 30-October 7, 1986, 347 persons in adjacent west Texas counties (Ector and Midland) contracted culture-confirmed Shigella sonnei gastroenteritis. A case-control study showed an increased risk of acquiring shigellosis in Ector County with eating at outlets of fast-food Restaurant A, and in Midland County with eating at Restaurant B or C. A second case-control study, of persons who had eaten at Ector County outlets of Restaurant A, showed an increased risk of acquiring shigellosis with eating foods containing shredded lettuce and tomatoes, which were served together (odds ratio = 68.8; 95% confidence interval 8.5-293.1). All implicated restaurants received shredded lettuce produced at one lettuce-shredding plant; two implicated restaurants did not receive tomatoes from the lot delivered to other implicated restaurants. The lettuce-shredding plant distributed shredded lettuce and intact lettuce; restaurants that received only intact lettuce were not involved in the outbreak. Investigation at the lettuce-shredding plant suggested that a food handler might have been the source of contamination and that the method of processing might have allowed cross-contamination to occur. In the laboratory, the outbreak strain of S. sonnei multiplied rapidly on shredded lettuce at 22 C and survived on refrigerated shredded lettuce for at least seven days. This outbreak, one of the largest outbreaks of Shigella infections in the United States in the last decade, indicates that a large, geographically widespread shigellosis outbreak can result from contaminated shredded lettuce that is distributed commercially.

From 1977-1986, a total of 331 laboratory confirmed cases of human brucellosis were reported in Texas. The annual number of cases ranged from 13 in 1977 to 84 in 1983. Males accounted for 66% of the cases. Cases ranged in age from one to 92 years, with 57% between the ages of 20 and 49 years. Brucella melitensis infections accounted for 66% of the bacteriologically confirmed cases. Infection with Brucella canis was identified in four patients. Annual incidence rates were higher in Hispanics in each age and sex group when compared with whites and blacks. Epidemiologic features of cases reported during 1977-1981 are dissimilar to features of cases reported during 1982-1986. In the first five years, a majority of cases (82%) were males, and a majority (54%) were white. Exposure to cattle or swine was reported for 72% of the cases. In the second five years, a majority (72%) of cases were Hispanic, and only 55% were males. Ingestion of unpasteurized goat milk products was reported for 67% of the cases during 1982-1986.

A single case of severe diarrhea on a floating Texas oil rig was followed two days later by what proved to be the largest outbreak of cholera in the United States in over a century. After isolation of toxigenic Vibrio cholerae El Tor Inaba of the typical United States phage type from the index patient's stool, the ensuing investigation detected 14 additional cases of cholera and one asymptomatic infection serologically. Infection was associated with eating rice on the oil rig on a particular day (P = 0.03) when an open valve permitted the rig's drinking-water system to be contaminated by canal water containing sewage (including that from the index patient) discharged from the rig. The rice had been rinsed in the contaminated water after cooking, and before being served it had been maintained at a temperature that allows V. cholerae 01 to multiply. Toxigenic V. cholerae 01 is persisting in the United States, and large common-source outbreaks of cholera can occur if proper sanitation is not maintained.

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