Cholera outbreak caused by drinking lakeshore water contaminated by feces washed down from a hill-side residential area: Kaiso Village, Uganda

Cholera is a bacterial diarrheal disease caused by Vibrio cholerae. On 15 October 2015, a cholera outbreak involving dozens of cases and 2 deaths was reported in Kaiso, a lakeshore fishing village. The district health department responded by setting up a treatment center and sensitizing the community. Despite initial response, the outbreak persisted, prompting a detailed epidemiological investigation to identify the source and mode of transmission and recommend evidence-based interventions to stop the epidemic. We defined a suspected case as onset of acute watery diarrhoea in a Kaiso Village resident from 1 st October 2015 onward; a confirmed case was a suspected case with Vibrio cholerae isolated from stool. We performed descriptive epidemiology to generate a hypothesis, and conducted a case-control study to compare exposure histories of 61 cases and 126 controls randomly selected among village residents (age ≥ 4 years in both groups). We conducted environmental assessment and obtained meteorological data from a local weather station. 123 suspected cases (2 deaths) were line-listed at the village’s cholera clinic. The initial 2 deceased cases had onset on 2 nd and 10 th October. Heavy rainfall occurred during 7–11 th . October, setting in a point-source outbreak which started on 12 th and peaked on 13 th October. Three water collection points (WCP) A, B and C were associated with the outbreak. 9.8% (6/61) of case-persons and 31% (39/126) of control-persons usually collected water from WCP A. In comparison, 21% (13/61) of case-persons and 37% (46/126) of control-persons usually collected water from WCP B (OR= 1.8, 95%CI: 0.64-5.3) and 69% (42/61) of case-persons and 33% (41/126) of control-persons from WCP C (OR=6.7; 95%CI=2.5-17). 100% (61/61) of case-persons and 93% (117/126) of control-persons never treated/boiled drinking water (OR=∞, 95%CI Fisher =1.0-∞). A gully channel from a hillside open defecation area washed down feces to the lakeshore at WCP C. This outbreak was caused by drinking lakeshore water contaminated by feces washed down a gully from the village. We recommended water boiling and treatment, fixing the broken piped-water system and constructing latrines. The outbreak was stopped by implementing treatment and boiling of drinking water at household level.