Factors associated with a cholera outbreak among island communities in Namayingo district, 2023

Abstract

Background: Uganda targets cholera elimination by 2030, yet outbreaks persist in high-risk fishing communities. Namayingo District in eastern Uganda has experienced recurrent outbreaks. This study assessed factors associated with the 2023 cholera outbreak in Namayingo to inform targeted and sustainable control measures. Methods: A case-control study was conducted on Sigulu and Bukana Islands. Due to incomplete matching data, the study was analyzed as an unmatched case-control design with a 1:3 case-to-control ratio. Suspected cases were persons aged ≥2 years with acute watery diarrhea and severe dehydration or cholera-related death; confirmed cases had Vibrio cholerae O1 or O139 identified by culture or PCR. Controls were residents with cholera-like symptoms who tested negative. Data were obtained from standardized case investigation forms and outbreak-response documents from the District Health Team and Ministry of Health. Bivariate analysis used Fisher’s exact tests, and multivariable analysis applied Firth logistic regression to address small sample bias and quasi-complete separation. Analysis was conducted using R (2024.12.1+563). Results: Seventeen cholera cases (6 confirmed, 11 suspected) were identified, with no deaths. The mean age was 20 years (SD 16.9), and 77% were female. The overall attack rate was 11 per 100,000, with 82.4% of cases clustered in Secho Village on Sigulu Island (localized attack rate: 74 per 100,000). Occupation, residence, and water treatment were significantly associated with infection. Students had higher odds of cholera compared to fisherfolk (aOR = 8.4; 95% CI: 2.1–33.7). Living in Sigulu increased infection odds (aOR = 6.4; 95% CI: 1.5–37.7). Treating drinking water reduced the odds of cholera (aOR = 0.17; 95% CI: 0.05–0.55). Conclusion: The outbreak was driven by geographic clustering, student vulnerability, and inadequate drinking-water treatment. Strengthening safe-water access, promoting household water treatment, and targeted health education are essential for preventing future outbreaks and achieving cholera elimination.