Outbreak of Norovirus Gastroenteritis in Elderly Evacuees After the 2007 Noto Peninsula Earthquake in Japan

To the Editor: On March 25, 2007, at 9:42 a.m. (Japan Standard Time), a strong earthquake occurred off the Noto Peninsula, near the west coast of this peninsula. The magnitude of this earthquake according to the the Japan Meteorological Agency was Mj6.9. In the quake, 337 people were injured, including one woman who died, and 1,683 homes were completely or partially destroyed. At least 2,600 displaced people went to evacuation centers provided by the government because of disruption of utility services and major traffic routes. On March 29, two evacuees suddenly developed stomachache, vomiting, and diarrhea. There were 74 evacuees (including 61 elderly persons) in the shelter. A medical aid team (consisting of 2 doctors expert in emergency medicine, 2 geriatricians, 2 intensive care nurses, and 2 clerical employees) from Kanazawa Medical University Hospital was sent to the shelter. Thirty-one evacuees with gastroenteritis, 29 of whom were aged 65 and older (mean 76±7), were examined and treated with parenteral hydration on April 2. Two subjects developed aspiration pneumonia and were admitted to the hospital. Testing using reverse-transcriptase polymerase chain reaction detected norovirus in stool specimens from the elderly patients in the evacuation center. The team immediately instructed all the evacuees on personal hand washing, gargling, and use of disinfectants on environmental surfaces to inhibit person-to-person transmission of the norovirus gene in the shelter. Fortunately, few cases of gastroenteritis were being reported in the center 1 week later. We investigated the morbidity rate of gastroenteritis in the evacuees in several shelters, including this evacuation center, who attended the clinic of the medical team from March 27 through April 24. The morbidity rates are shown in Table 1; the peak rate was 6.6% 9 days after the onset of the quake. Noroviruses (formerly called small round structured virus or Norwalk-like virus) are the prototype of caliciviruses (chalice=cup or beaker from the Latin word calix).1 They are single-strand, nonenveloped ribonucleic acid viruses and measure 28 to 35 nm. The norovirus was first discovered in 1968 in Norwalk County, Ohio.2 Electron microscopic examination of the virus shows a characteristic chalice-shaped surface.3 An outbreak of norovirus gastroenteritis has recently been reported in association with contaminated flood water in Salzburg in 2005.4 Elderly subjects are one of the high-risk populations susceptible to norovirus infection. Outbreaks of norovirus gastroenteritis were recently described in 236 healthcare facilities for elderly people during the winter of 2004/05 in Japan.5 Genetically close conventional genotype GII-4 strains were deemed to have caused them, although new variant strains were observed in Europe in 2003.6 The environmental status after natural disasters (earthquake, flood, and hurricane) induces an increased risk for infectious diseases, including gastrointestinal and respiratory illnesses. Because access to functioning flush toilets and potable water is disrupted, it is recommended that evacuation centers be prepared to address the considerable demands on medical staff, janitorial services, and maintenance of personal hygiene.7 Elderly individuals who are unable to evacuate affected areas because of underlying illnesses might be more susceptible to infectious diseases. In addition, crowding and unsanitary conditions would induce transmission of infectious diseases once evacuees have relocated to shelters. The widespread outbreak of norovirus gastroenteritis in evacuees of Hurricane Katrina residing in a large megashelter in Houston, Texas,8 as well as our experience of norovirus infection in the public health community after the 2007 Noto Peninsula earthquake suggests the need to establish more-effective measures to control and prevent this highly contagious gastrointestinal disease. Conflict of Interest: Dr. Morimoto was supported in part by a grant-in-aid for scientific research from the Ministry of Health, Labour and Welfare of Japan. Dr. Takahashi was supported in part by a grant to promote research from Kanazawa Medical University (S2005-5). There is no conflict of interest regarding the present study. Author Contributions: Shigeto Morimoto and Takashi Takahashi contributed to study concept and design. Koji Nomura, Hiroshi Murai, Takeshi Nakahashi, Satoru Mashiba, and Yukihiro Watoh performed acquisition of subjects and data. Koji Nomura, Hiroshi Murai, and Shigeto Morimoto analyzed and interpreted the data. Takashi Takahashi and Shigeto Morimoto prepared the letter. Sponsor's Role: The sponsors had no role in this letter.