Investigation of cholera outbreak in Rayong Province, Thailand, 4th October 2015–5th January 2016

Abstract

Background: Cholera is one of a fatal infectious diseases and has potential to cause prolong and widespread epidemic. In October 2015, the Department of Disease Control, Thailand, received a notification from Rayong Province regarding 17 confirmed cholera infected person. An investigation was conducted to identify source and recommend prevention and control measures.
Methods: Descriptive study was conducted. We reviewed medical records and investigation forms of the cases, interviewed initial and new cases and performed active case finding. Cases were defined as people who resided in Rayong province and had loose or watery stool during 24 September 2015 to 5 January 2016 with rectal swab cultures found Vibrio cholerae O1 or O139. Laboratory study and environmental study were also performed.
Results: During 4 October 2015 to 5 January 2016, there were 103 cholera infected people (88 cases, 15 asymptomatic carriers), with 2 fatal cases. All were from Vibrio cholerae O1 El Tor Ogawa. The outbreak started at Paknam Subdistrict, Muang district, then further spread to Klaeng, Ban Khai and Nikhom Phatthana districts. Majority of the cases were Cambodian migrant workers who worked in the ships and fishing ports. Most of them had poor sanitation, used untreated water from Rayong River to prepare foods and usually ate raw seafood. Residual chlorine in tap water was less than 0.2 ppm. All foods and water samples from high risk areas were negative for Vibrio cholerae O1. During the initial 2 weeks, the control measures were not effective due to lack of human resource. After level up the EOC to the provincial level that leaded to several improvement as well as changed strategy to pro-active approach, the outbreak was subside.
Conclusion: This cholera outbreak was prolong and expanding to several districts. Main source of the outbreak was the consumption of raw or semi-raw seafood from Rayong River. Rapid and systematic response, including intensive and effective risk communication to public, systematic improvement of risky sanitation and well cooperation among key stakeholders were the keys of success in controlling this outbreak.