RESUMO
OBJECTIVE: To study epidemiologic characteristics of a cholera outbreak involving mainly Myanmar migrants living in overcrowded conditions with poor sanitation in a Thai-Myanmar border district, in 2007. MATERIAL AND METHOD: Both passive and active case surveillances were carried out in Mae Sot District, Tak Province since the beginning of the outbreak. Samples of various types of drinking and non-drinking water from the infected areas, communal waters, and some selected foods were analyzed for the presence of cholera contamination. A case-control study was conducted to determine the vehicle of cholera transmission among Myanmar migrants in one municipal community with a cluster of 72 cholera cases. Preventive and control measures were primarily carried out by trained migrant health volunteers and workers. RESULTS: Between May and October 2007, 477 cholera cases of biotype El Tor, serotype Inaba, were identified in the district. The majority of them (93.1%) were detected by active case surveillance in the communities. None died in this outbreak. Most (84.9%) were Myanmar migrants and the remainder were local Thai residents. The infection rates of cholera were significantly greater in communities with known passive cases than in those with no such cases. Three samples of seafood illegally imported from Myanmar were positive for cholera of the same biotype and serotype. Fifteen of 324 (4.6%) food handlers in the district were found to carry V. cholerae O1. A case-control study in one municipal community revealed a significant association between infection and frequently having food purchased from one infected food handler. CONCLUSION: Active case finding and implementation of control measures by the assistance of trained migrant health volunteers and workers might reduce the morbidity and mortality in this population.