Jpn. J. Infect. Dis., 59, 2006

Laboratory and Epidemiology Communications

Shigellosis in Kobe City, Japan, after School Excursion
to Malaysia and Singapore
Tomoki Kimura*, Akira Inoue, Yasuto Kawakami and Chika Shirai1
Preventive Health and Hygiene Control Division, Kobe Public Health Center, Kobe 651-8570 and1
Health and Welfare Division, Public Health and Welfare Department,
Hyogo Ward Office , Kobe 652-8570, Japan
Communicated by Haruo Watanabe(Accepted May 23, 2006)

unboiled water, juice, sliced fruits, salad, milk, ice cream,
rice ball, and so on.
When S. sonnei was isolated from the fecal cultures of thesix students, all six were recommended to have a medicalconsultation, followed by sterilization of their houses anda full health check, including a fecal culture test for theirfamily members. However, no family members developed
any symptoms of diarrhea and all fecal culture tests werenegative.
The first reported patient (index case) was already free fromsymptoms of diarrhea on the reported day of January 31; therefore, antibiotics were not prescribed throughout the courseof his recovery. Fecal culture was negative on both January
31 and February 6, which led to a diagnosis of full recovery
from the pathogenic bacteria. However, a fecal culture test
done on February 13 (20 days after his return) again detected
S. sonnei despite the continuous absence of any symptoms
since his return from the excursion.
As a secondary infection, his father developed fever anddiarrhea on February 12, and 2 days later visited a medical
facility for a fecal culture test. The antibacterial medication
cleared his symptoms smoothly, while S. sonnei was isolated
from his fecal culture on February 18. Thus, this secondarycase was an intrafamilial infection from the son, who had
never been treated with antibacterial drugs. Probably, theson continued to excrete S. sonnei in small amounts withoutclinical signs. In addition, this family had not been fully
cooperative with the Kobe Public Health Center before thefather’s illness; sterilization of their home and guidance on
clean hand-washing had not gone well. This further suggested
the inducement of secondary infection.
On the other hand, the high school was cooperative in thesterilization and in carrying out health guidance on topics
such as adequate hand-washing for all years of students. A
subsequent health observation verified normal conditions, thus
excluding any possibility of secondary infection.
Recently, a number of schools in Japan have chosen overseas destinations for their school excursions. To prevent
infection, schools and boards of education ought to convey
the basic principles of hygiene before the trip begins. While
traveling abroad, students need to pay more attention to thecontents of their meals and to washing their hands, in addition to understanding the importance of medical consultation
at quarantine stations upon their return, if necessary.

Shigella sonnei was isolated from six high school students
in Kobe, Japan after a January 2006 excursion to Malaysia
and Singapore and from a member of one sudent’s family inKobe.
A medical facility reported a case of shigellosis to the Kobe
Public Health Center on January 31, 2006. Five days earlier
the patient, a 17-year-old boy, had complained of a fever(39°C), diarrhea and abdominal pain. He did not receive any
antibacterial treatment, but his stool was examined in a fecal
culture test. His symptoms and signs subsided on January
28. However, S. sonnei was isolated in the fecal culture test.
The patient had taken part in a school excursion to Malaysia and Singapore from January 21 to January 25. They left
Kansai International Airport on January 21 and arrived
in Malaysia via Singapore; they visited Kuala Lumpur,
Malacca and Johor Bahru, then returned to Singapore on themorning of January 24. They left Singapore late at night andarrived at Kansai early in the morning of January 25.
This shigellosis was suspected to have been imported toJapan via the excursion, which included 332 students, 16teachers and 5 couriers. After the first patient was diagnosed,
all other participants in the excursion were given a fecal
culture test, and S. sonnei was isolated from an additional
five students. Moreover, a retrospective health check interview revealed that 11 students suffered from diarrhea during
the excursion and 11 students developed diarrhea after theexcursion. However, nobody reported their symptoms atthe quarantine station upon their return to Japan. None ofthe teachers or couriers had any symptoms, and their fecal
cultures were negative.
The five culture-positive students developed a fever (38 40°C range) and diarrhea upon their return to Japan (January25) or on the next day. Two of them saw a physician but had
no fecal examination. When the Kobe Public Health Center
investigated these five students, they were already free fromsymptoms.
All six of the culture-positive students stayed at the same
hotel and dined at the same facilities. Most of the meals
were served smorgasbord style, so it was rather difficult toremember which foods were eaten or to identify the common
suspect foods consumed by these six students. In this excursion, the common carriers of shigellosis are thought to include*Corresponding author: Mailing address: Preventive Health andHygiene Control Division, Kobe Public Health Center, Kumoidori 5-1-1, Chuou-ku, Kobe 651-8570, Japan. E-mail: tomoki_
kimura@office.city.kobe.jp

This article appeared in the Infectious Agents Surveillance
Report (IASR), vol. 27, p. 68, 2006 in Japanese.
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