Cholera outbreak investigation in Adamawa state, Nigeria, June 2021 - December 2021: An unmatched case-control study.

BACKGROUND: Cholera is a major public health challenge in Nigeria. On 09 September 2021, the Adamawa State Ministry of Health confirmed an outbreak affecting 12 local government areas (LGAs). AIM: To describe the outbreak and identify risk factors. SETTING: Community-based in Adamawa State, Nigeria (30 June 2021 - 01 December 2021). METHODS: We described the State cholera line list (30 June 2021 - 01 December 2021) and estimated case fatality and attack rates. We conducted an unmatched case-control study in seven LGAs, involving 66 laboratory-confirmed cases and 120 asymptomatic neighbourhood controls. We collected data on demographics, clinical history, practices and risk factors using interviewer-administered questionnaires. We executed univariate, bivariate and multivariate analyses to estimate adjusted odds ratios (aORs) and 95% confidence intervals (CIs). RESULTS: Of 1332 cases reported across 12 LGAs, we recorded an overall case fatality rate (CFR) of 3.6%. We recorded the highest CFR (16.7%) in Song and the attack rate (N = 239.6/100 000) in Numan. Children aged 5-14 years were most affected. The median age was 24 years for cases (range: 1-76) and 32 years for controls (range: 5-70). Males accounted for 54.5% (cases) and 53.3% (controls). Independent risk factors were age < 10 years (aOR = 9.7; 95% CI: 2.6-34.9) and consumption of street-vended noodles (aOR = 7.0; 95% CI: 1.4-34.8). CONCLUSION: The outbreak disproportionately affected children with unregulated food sources, contributing significantly. Public health interventions included hygiene education and chlorine distribution. Strengthening food safety regulations and sustaining hygiene promotion were recommended to mitigate future outbreaks. CONTRIBUTION: The study supports Nigeria's Cholera Control Programme in refining hygiene strategies, regulating street food safety and targeting high-risk groups, such as young children.