Retrospective Field Investigation of a Cholera Case in Bangladesh Following IHR Notification

<i>Background:</i> Sporadic occurrence of cholera is an epidemiological challenge to identify the source. In last week of November 2016, the World Health Organization (WHO) reported a 32-year-old Bangladeshi male overseas worker developed acute watery diarrhoea en route to Oman and was diagnosed with cholera. As the focal institute of the International Health Regulation (IHR), the Institute of Epidemiology, Disease Control and Research (IEDCR) initiated a retrospective investigation to identify possible sources of <i>Vibrio cholerae</i> exposure at the patient's departure. <i>Methods:</i> The investigation was conducted from December 2-4, 2016. We communicated with the patient's relative and traced the last 6 days of his stay in Bangladesh and his journey from his home village Bheramara subdistrict, Kushtia, to the Hazrat Shahjalal International Airport, Dhaka City, before boarding the aircraft. We interviewed with family members and tracked the patient's food and water exposures during the incubation period. Local subdistrict hospital admission data were reviewed to assess any concurrent outbreak in the locality. Water samples were collected and tested from identified consumption sites. Environmental observations focused on the water distribution infrastructure. <i>Results:</i> Patient was apparently healthy the day before his journey. Patient and his younger brother travelled through public transport to the capital and stayed overnight in a hotel near the airport to catch his flight the next day. Both of them drank supplied water in the residential hotel and restaurant near the airport. The subdistrict hospital surveillance data showed no unusual increase in diarrhoea admissions in patient's community. Five water samples that were collected from village and roadside vendors were tested negative for fecal contamination. However, water samples, collected from hotel and restaurants near the airport, showed the presence of fecal <i>Echerichia coli.</i> Environmental assessments revealed leakages in the water supply lines of the city corporation in Ashkona area. <i>Conclusion:</i> Although not confirmed, the most likely source of the sporadic cholera <i>Vibrio cholerae </i>infection was the contaminated supply water in hotels or restaurants near the airport. We recommend that hotels and restaurants regularly chlorinate their underground and overhead water tanks. The Dhaka city corporation office need to ensure a safe water supply line without any leakage. We also recommended providing health education regarding safe drinking water to the overseas workers.