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Hainanese chicken rice (cooked rice mixed with chicken fat and served with sliced chicken and cucumber) is a well-known Chinese dish in Southeast Asian countries. We report two consecutive outbreaks of cholera associated with consumption of chicken rice among attendants of two meetings in northwestern Thailand in April 2010. Active case finding was carried out among persons who attended the meetings and in the community. Environmental investigation was conducted at the implicated food shop and in the affected areas. The first outbreak involved 17 cholera cases (35.4%) among 48 attendants and 16 cases in the community. The onset of symptoms was between April 19 and 23, 2010. People who ate the chicken rice had a higher attack rate of infection than those who did not. All 12 food handlers at the implicated food shop were screened for cholera infection by rectal swab culture; 3 were culture-positive. Although the food shop was closed temporarily following the outbreak, some chicken rice was produced and served at the second meeting and caused 11 more cases (23.4%) among 47 meeting attendants. All cholera isolates obtained from patients and food handlers were V. cholerae O1, biotype El Tor, serotype Ogawa, and had similar antibiograms and genetic patterns by pulsed-field gel electrophoresis. The chicken rice which was possibly contaminated by an infected food handler served as the vehicle of transmission. A repeat cholera outbreak caused by the same vehicle can occur when control measures are not adequately followed.

On August 5, 2005, a private hospital reported a large number of students with gastrointestinal illness from the same school in Bangkok, Thailand. The Bureau of Epidemiology along with the Bangkok Metropolitan Administration investigated this outbreak, to determine risk factors, identify the source of infection and possible causative organism, and recommend prevention and control strategies. A case was defined as a person who was studying or working at School A and who developed abdominal pain, diarrhea, nausea or vomiting during the five-day period of August 4 to 8, 2005. A descriptive study was carried out for active case-finding, medical records review, and case interviews. We conducted the retrospective cohort study among third and fourth grade students. Stool samples were collected and tested at the Thai National Institute of Health and at private hospital laboratories. The overall attack rate was 37%. Main symptoms were diarrhea, fever, headache, abdominal pain, vomiting, and nausea. The highest attack rate (63%) was among fourth-grade students. Based on food-history data collected from ill and well students, a multiple logistic regression analysis showed that a mixed chicken and rice dish served for lunch on August 4 was associated with illness (OR 3.28, 95% CI 1.46-7.36). Among stools samples from 103 cases, Shigella group D was found in 18 cases, Salmonella group C in 5 cases, and Salmonella group E in 2 cases. This food borne outbreak of gastroenteritis was most likely caused by Shigella spp although the possibility of mixed contamination with Shigella and Salmonella spp cannot be ruled out. Food borne outbreaks such as this can be prevented through simple and effective hygienic measures.