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

Laboratory and Epidemiology Communications

A Norovirus Outbreak of Gastroenteritis Linked to Packed Lunches
Naomi Sakon*, Kenji Yamazaki, Tomoko Yoda, Masashi Kanki, Toru Otake and Teizo Tsukamoto
Department of Infectious Diseases, Osaka Prefectural Institute of Public Health, Osaka 537-0025, Japan
Communicated by Tatsuo Miyamura(Accepted June 14, 2005)
remaining 13 on the 13th of December. NoV GI was positivein 6 of the 16 (38%) samples. Four of 6 staff members boiledor grilled food, while the other 2 filled the lunch boxes.
However, it remains unknown whether the 2 staff membersthat filled the contaminated lunch boxes were positive for
NoV at that time.
A comparison of the nucleotide sequence of positive
samples from patients and staff members and those of reference strains of NoV GI (1,2) showed 98 - 99% identity with
SaitamaKu19aGI/01/JP, which belongs to GI.12.
It was concluded that this NoV outbreak was due tocontaminated box lunches. This result indicates the difficulty
involved in controlling and preventing NoV transmission; italso highlights the importance of worker health management
and hygiene programs for catering staff.

A foodborne outbreak that occurred in Osaka in December
2004 was linked to a catering company that prepared packed
lunch boxes. Norovirus (NoV) was found as the causative
agent of gastroenteritis, which involved 91 staff members of
8 different companies. Catering staff were also found to bepositive for NoV.
On the 5th of December 2004, the Nara City Public HealthCenter received a report of an outbreak of gastroenteritis from“H” company (Table 1). Interviews were conducted and questions were asked about the victims’ symptoms, foods eaten,
eating place, etc. A common meal, i.e., contaminated packed
lunch boxes, was suspected to be the cause of this illness.
The meal was prepared on the 3rd of December by a catering
company located in Osaka that makes about 8,000 box lunches
per day. Box lunches made on the 3rd of December werecatered to 221 companies, which included 4,300 box lunches
in Osaka, Nara and Hyogo. Ninety-one staff members in 8
companies became ill, showing signs of diarrhea, vomiting
and tenesmus (Table 1). Twenty-three stool specimens werecollected from ill people and examined for causative agentsof gastroenteritis in the Osaka Prefectural Institute of Public
Health Laboratory. NoV GI was detected in 21 of thesesamples by reverse transcriptase-polymerase chain reaction(RT-PCR) using G1F1/G1SKR primers (directed against theN-terminal of the capsid region). The suspected contaminatedbox lunches had been prepared between 3:30 and 4:30 a.m.;
however, there was also the possibility that the lunches had
been contaminated by secondary workers. Therefore, stool
samples were collected from 16 of 71 secondary workers that
had worked around midnight on the 3rd of December andwere examined for the presence of NoV. Three of the 16
samples were collected on the 8th of December and theThe authors extend their gratitude to the staff of the Nara
City, Moriguchi City and Takatsuki City of Public Health.
This article appeared in the Infectious Agents Surveillance
Report, vol. 26, no. 4, p. 98, 2005 in Japanese.
REFERENCES
1. Kageyama, T., Shinohara, M., Uchida, K., Fukushi, S.,
Hoshino, F., Kojima, S., Takai, R., Oka, T., Takeda, N.
and Katayama, K. (2004): Coexistance of multiple genotypes, including newly identified genotypes, in outbreaksof gastroenteritis due to norovirus in Japan. J. Clin.
Microbiol., 42, 2988-2995.
2. Katayama, K. (2004): Norovirus infection. Infect. Dis.
Wkly. Rep., no. 11, 14-19 (in Japanese).

Table 1. Number of illness and detection of NoV by companies who received the packed lunch
Company

No. of packed lunch

No. (%) with symptoms

No. of stool samples examinedABCDEFGH

143301072888

11 ( 78.6)
2 ( 66.7)
13 ( 13.3)
7 ( 70.0)
3 ( 42.9)
2 (100.0)
6 ( 75.0)47 ( 53.4)

8154
104
1071541037Total

162

91 ( 56.2)

3328 (84.8%)*Corresponding author: Mailing address: Department of Infectious Diseases, Osaka Prefectural Institute of Public Health, 13-69 Nakamichi, Higashinari-ku, Osaka 537-0025, Japan. Tel:+81-6-6972-1321, Fax: +81-6-6972-2393, E-mail: nsakon@iph.
pref.osaka.jp
253

No. of sample positive