[On the outbreak of Shigellosis in Tokyo, 1992]

In 1992, the number of cases of shigellosis in Tokyo increased remarkably, and a total of 10 separate outbreaks were confirmed. Except for 1 series where the causative strains was Shigella flexneri 3a, the other 9 outbreaks were caused by Shigella sonnei. Of note, 7 outbreaks were familial with less than 5 patients. The remaining 3 outbreaks occurred in a restaurant, a school and the dormitory of an orphanage, in which the organism was detected in 6 to 14 patients. In 4 of the familial outbreaks occurring in distant areas during August, ark shell was presumed to be the vehicle by epidemiological investigations and laboratory examinations. Analysis of isolates such as the antibiotic resistance pattern, plasmid profile, or colicine type in Shigella sonnei was useful in clarifying the commonality of each case and identifying the vehicle or transmission.