Outbreak of enterohemorrhagic Escherichia coli O111 among high school participants in excursion to Korea.

*Corresponding author: Mailing address: Ishikawa Prefectural Institute of Public Health and Environmental Science, 1-11 Taiyohgaoka, Kanazawa 920-1154, Japan. E-mail: hokan-04@ pref.ishikawa.jp On July 7, 2004, a health center in Kanazawa City received a report of enterohemorrhagic Escherichia coli (EHEC) O111 (VT1 and 2) infection. The patient was a high school student who participated in a school excursion to Korea from June 28 to July 1. Upon investigation of the 358 students who went to Korea for the school excursion, 107 responded that they had similar intestinal symptoms. The onset of the symptoms of the patients was distributed from June 28 to July 8 with a peak on July 2 (Fig. 1). As few students who did not participate in the excursion had such symptoms, infection during the excursion to Korea was strongly suspected. From July 8 to 23, the health centers responsible for the communities with the patients examined stool specimens from 358 students, 16 teachers and 4 travel agency guides who went to Korea for the excursion, and from 337 family members of the EHEC-positive patients. EHEC was isolated from 103 individuals (98 students, 4 teachers and one family member). The dominant serotype of the isolated EHEC was O111, isolated from 78 individuals. O26, O146, O157, OUT and other serotypes were also isolated. There were individuals infected with two serotypes (Table 1). Among isolates of the same serotype, the pattern of pulsed-field gel electroFig. 1. Number of students with the first sign of infection. 0 5 25