Successful multi-partner response to a cholera outbreak in Lusaka, Zambia 2016: a case control study

Abstract

Background: A Cholera outbreak was reported in Lusaka District between February and May 2016, with 1,079 cases and 20 deaths recorded in the per-urban areas. Bauleni catchment area alone reported 441 (40.9%) case patients with case fatality rate of 4 (0.9%). Bauleni clinic was one of the three established cholera treatment centres (CTC) and other two being Kanyama and Matero Health Centres. Ministry of Health engaged partners that conducted a multi-intervention response to the outbreak. This study is aimed at identifying factors associated with the outbreak.

Materials and methods: We conducted a case-control study, at the ratio 1:3, to identify risk factors associated with cholera outbreak. We identified cases of cholera through the cholera register at Bauleni health centre and randomly selected population based controls being residents of Bauleni Township without watery diarrhoea. The standard case definition for suspected cholera case was any person of any age with profuse, effortless watery diarrhoea (three or more stools in 24 hours), with or without vomiting. Aconfirmed cholera case was defined as any person suspected to have cholera with a positive  laboratory result. Univariate and multivariate analysis was performed using Epi-Info version 3.5.4 and Stata version 11.2.

Results: On the Cholera Treatment Centre surveillance case-patients register, out of 441 cases, 241 (54.6%) cases were male while 200 (45.4 %%) cases were female, with an attack rate of 14.8/1,000 population and 4 (0.9%) fatalities. The study participants, who included 49 casepatients and 151 controls, had mean-age of 31 years [range, 29-34 years]. Positive Vibrio in stool cholera was associated with drinking inadequately treated borehole water [Adjusted OR=0.79; 95% CI (0.10-6.04), p>0.05]. This odds ratio was adjusted for level education and gender to control and account for any confounding. Though this finding was not statistically significant at p>0.05, the laboratory result was biologically significant as vibrio cholerae was isolated in the borehole water. Drinking treated water was protective [Adjusted OR 0.13; 95% CI (0.05-0.31, p<0.05].

Conclusion: Improving methods that promote safe drinking water are likely to be effective measures in averting future cholera outbreaks in this setting.

Keywords: Cholera, Lusaka, risk factors, case control