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

Laboratory and Epidemiology Communications

Shigella sonnei Outbreak among Japanese Travelers Returning from Hawaii
Jun Terajima, Naoki Tosaka1, Kumi Ueno1, Kazutoshi Nakashima1, Paul Kitsutani1,Mary K. Gaynor2, Sarah Y. Park2 and Haruo Watanabe*
Department of Bacteriology, and 1Infectious Disease Surveillance Center,
National Institute of Infectious Diseases, Tokyo 162-8640, Japan, and2
Disease Outbreak Control Division, Hawaii Deparment of Health, Hawaii 96813, USA
Communicated by Yoshichika Arakawa(Accepted July 13, 2006)
On August 25, 2004, a traveler returning from Hawaii
became ill with shigellosis. By September 2, it was revealed
that seven other individuals who had traveled to Hawaii withthe patient were also infected. By September 8, a total of 15
epidemiologically linked cases had been reported through theNational Epidemiological Surveillance of Infectious Diseases(NESID) program. Simultaneously, our informal inquiry with
the Hawaii Department of Health confirmed that there wereother reports of shigellosis associated with U.S. domestic
and international air travel from Hawaii. Through NESID inJapan, two cases were suspected to be associated with airtravel from Hawaii among 16 cases of shigellosis during the35th week of 2004. Thirteen (43%) among 30 cases in the36th week were suspected to be associated with air travelfrom Hawaii. No cases were reported after the 37th week
(Figure 1). All 15 patients boarded N airline at Honolulu
airport in Hawaii between the 22nd and 24th of August andno secondary transmission of the infection was confirmed.
All 15 cases had diarrhea, 7 (47%) had abdominal pain, and13 (87%) had fever. Three were hospitalized, but no fatalcase was reported. Shigella sonnei was isolated from thestool samples of all 15 cases. The patients were spread overJapan, residing in Wakayama, Mie, Osaka, Chiba, Kanagawa,Kagawa, and Hyogo Prefectures as well as in the Tokyo metropolitan area. Combining the results of the Japanese and U.S.
epidemiological investigations of the outbreak, it is most likelythat salad served on-board the associated airlines may be thesource of the infection. Isolates from all 15 patients wereanalyzed by pulsed-field gel electrophoresis (PFGE) according to the standardized PFGE protocol that was developedfor PulseNet by the U.S. Centers for Disease Control andPrevention (CDC) (1,2). Among the 15 strains restricted withXbaI, nine strains showed an h1 pattern, five showed an h2
pattern that differed from h1 by one band, and one strain
showed an h3 pattern that differed by two bands (Figure 2).
The strains with the h1 pattern and h2 pattern restrictedwith BlnI showed slightly different patterns respectively
but indistinguishable within each pattern (data not shown).
In addition to an informal exchange of outbreak information
with investigators in Hawaii, we received an urgent noticefrom the CDC’s PulseNet International on September 4
regarding a shigellosis outbreak associated with air travel fromHawaii, along with tiff images of the PFGE patterns of theFig. 1. Number of reports of shigellosis in Japan through NESID during
the week of 31st to 40th in 2004. The places/nations where the patients
presumably acquired the infection are represented by different patterns.

Fig. 2. Representative PFGE patterns of Shigella sonnei isolates fromair-travel related cases. Lanes h1 to h3 are isolates from the patients.
Lanes M are Salmonella Braenderup H9812 strain used as a molecularsize marker.

associated Shigella isolates. Two major patterns were also
observed in these tiff images; moreover, based on PFGE analysis of strains from the CDC and those from our laboratory, weconfirmed that the two sets of patterns were indistinguishable.
Cooperation with our U.S. partners responsible for laboratory and epidemiological investigation was extremely useful*Corresponding author: Mailing address: Department of Bacteriology, National Institute of Infectious Diseases, Toyama 1-231, Shinjuku-ku, Tokyo 162-8640, Japan. Tel/Fax: +81-3-52851171, E-mail: haruwata@nih.go.jp
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for prompt recognition and investigation of this outbreak andfor taking preventive measures. For any international outbreak
investigation, it is essential to reinforce the global frameworkof information exchange.

Report (IASR), vol. 27, p. 64, 2006 in Japanese.
REFERENCES
1. Swaminathan, B., Barrett, T. J., Hunter, S. B., Tauxe, R.
V.; CDC PulseNet Task Force (2001): PulseNet: themolecular subtyping network for foodborne bacterialdisease surveillance, United States. Emerg. Infect. Dis.,7, 382-389.
2. Hunter, S. B., Vauterin, P., Lambert-Fair, M. A., VanDuyne, M. S., Kubota, K., Graves, L., Wrigley, D.,
Barrett, T. and Ribot, E. (2005): Establishment of auniversal size standard strain for use with the PulseNet
standardized pulsed-field gel electrophoresis protocols:
converting the national databases to the new size standard. J. Clin. Microbiol., 43, 1045-1050.

We thank Desmond Jennings, PulseNet USA for providing us valuable information of the U.S. isolates and sending
us the strains. We thank all investigators of prefectural andmunicipal public health institutes for providing us samples
and information. We also thank Mses. Shoko Imamura, ReikoSuzuki, Nobuko Takai, and Mr. Yasunori Saito for their help
in PFGE analysis.
This work was supported in part by the grant-in-aid from
Minstry of Health, Labour and Welfare, Japan (grant nos. H17Sinkou-ippan-019 and H18-shinko-ippan-016).
This article appeared in the Infectious Agents Surveillance283