A Prolonged Cholera Outbreak Caused by Drinking Contaminated Water from a Stream, Kyangwali Refugee Settlement, Hoima District, Western Uganda: February-May 2018

Abstract Background: On 23 February 2018, the Uganda Ministry of Health (MOH) declared a cholera outbreak affecting more than 60 persons in Kyangwali Refugee Settlement, Hoima District, bordering the Democratic Republic of Congo (DRC). We investigated to determine the outbreak scope and risk factors for transmission, and recommend evidence-based control measures. Methods: We defined a suspected case as sudden onset of watery diarrhoea in a person aged ≥2 years in Hoima District, 1 February-9 May 2018. A confirmed case was a suspected case with V. cholerae cultured from a stool sample. We found cases by active community search and record reviews at Cholera Treatment Centres. We calculated case-fatality rates (CFR) and attack rates (AR) by sub-county and nationality. In a case-control study, we compared exposure factors among case- and control-households. We conducted an environmental assessment in the refugee settlement, including testing of water samples from stream water, tank water, and spring water for presence of fecal coliforms. We tested suspected cholera cases using cholera Rapid Diagnostic Test (RDT) kits followed by culture for confirmation. Results: We identified 2,122 case-patients and 44 deaths (CFR=2.1%). Case-patients originating from DRC were the most affected (AR=15/1000). The overall attack rate in Hoima District was 3.2/1,000, with Kyangwali sub-county being the most affected (AR=13/1,000). The outbreak lasted 4 months, which was a multiple point-source. Environmental assessment showed that a stream separating two villages in Kyangwali Refugee Settlement was a site of open defecation for refugees. Among three water sources tested, only stream water was fecally-contaminated, yielding >100 CFU/100ml. Of 130 stool samples tested, 124 (95%) yielded V. cholerae by culture . Stream water was most strongly associated with illness (OR=14.2; CI=1.5-133), although tank water also appeared to be independently associated with illness (OR=11.6; CI=1.4-94). Persons who drank tank and stream water had a 17-fold higher odds of illness compared with persons who drank from other sources (OR=17.3, CI=2.2-137). Conclusions: Drinking contaminated stream water was associated with cholera outbreak. We recommended boiling drinking water, increasing latrine coverage, and provision of safe water by the District and United Nations High Commissioner for Refugees.