Jpn. J. Infect. Dis., 58, 2005

Laboratory and Epidemiology Communications

Outbreak of Enterohemorrhagic Escherichia coli O111 among High School
Participants in Excursion to Korea
Kazue Kato, Ryoko Shimoura, Kinuyo Nashimura, Kayo Yoshifuzi, Ken Shiroshita,
Noboru Sakurai, Hiroe Kodama1 and Sanae Kuramoto1*
Health Center of Kanazawa City, Kanazawa 920-8533 andIshikawa Prefectural Institute of Public Health and Environmental Science, Kanazawa 920-1154, Japan1

Communicated by Haruo Watanabe(Accepted September 20, 2005)
On July 7, 2004, a health center in Kanazawa City receiveda 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 wentto Korea for the school excursion, 107 responded that they
had similar intestinal symptoms. The onset of the symptomsof the patients was distributed from June 28 to July 8 with apeak on July 2 (Fig. 1). As few students who did not participate in the excursion had such symptoms, infection duringthe excursion to Korea was strongly suspected.
From July 8 to 23, the health centers responsible for thecommunities with the patients examined stool specimens from358 students, 16 teachers and 4 travel agency guides whowent 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

25

Number of patients/day

20

15

10

50

6/28

6/29

6/30

7/1

7/2

7/3

7/4

7/5

7/6

7/7

7/8

during excu rsion
DateFig. 1. Number of students with the first sign of infection.

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 isolatesof the same serotype, the pattern of pulsed-field gel electro-*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.jp332

Jpn. J. Infect. Dis., 58, 2005
Table 1. Serotypes of isolates from 103 patients (including family members of the excursion participants)
Serotype

Students positive

Teachers spositive

Family members positive

Total (with symptom)

O111:HNM (VT1, 2)
O26:H11 (VT1)O146:H19 (VT2)O157:H7 (VT1, 2)
O169:H19 (VT1)O103:H2 (VT1)
OUT:H18 (VT2)
OUT:H19 (VT1)
OUT:H25 (VT1)
OUT:H33 (VT1)O111:HNM (VT1, 2) O26:H11 (VT1)O111:HNM (VT1, 2) O169:HNM (VT1)O111:HNM (VT1, 2) O169:H19 (VT1)696216511113113173 (53)
6 ( 2)
2 ( 1)
1 ( 1)
7 ( 2)
5 ( 2)
1 ( 1)
1 ( 1)
1 ( 0)
1 ( 0)
3 ( 3)
1 ( 0)
1 ( 1)

Total

98

4

1103 (67)1phoresis (PFGE) of XbaI-digested chromosomal DNA was
identical (data not shown). In one case, we found the same
PFGE pattern for EHEC O111 isolated from a patient and his
younger brother, which suggested familial secondary infection.
The source of infection was not identified, as investigation isdifficult in foreign countries including Korea. The students
recalled that they consumed insufficiently cooked meat andgravy in which the raw meat was soaked, sometimes in street
restaurants.
School excursions abroad have become frequent, but it

appears that schools are ill prepared for the risk of infections
during such excursions. Health risk management planningshould be incorporated in the planning of excursions.
We thank Prof. Yoshikura, Emeritus Researcher of theNational Institute of Infectious Diseases, for advice on preparing the manuscript.
This article appeared in the Infectious Agents Surveillance
Report, vol. 26, 141-142, 2005 in Japanese.

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