Cholera outbreak in Niger State Nigeria, May to August 2021: An unmatched case-control study

Introduction: Cholera is an infectious disease characterized by acute watery diarrhea. It is caused by the ingestion of food or water contaminated with the toxigenic strains of Vibrio cholerae serogroups O1 or O139. On May 14, 2021, a case of cholera was reported from Gurara Local Government Area of Niger State. A Rapid Response Team was deployed immediately to describe the outbreak, determine its source, and risk factors, and institute control measures. Methods: We defined a suspected case of cholera as any person with acute watery diarrhea with or without vomiting living in Niger State from 14 May to 30th August 2021. We reviewed routine surveillance data obtained from the Integrated Disease Surveillance and Response (IDSR)and conducted active case searches in hospitals and communities. We calculated attack rates (AR) and case fatality rates (CFR) and generated an epi curve and spot maps. We conducted a case-control study using a structured interviewer-administered questionnaire to collect sociodemographic, clinical, and hygiene practice data from 67 cases and 134 controls. We tested 67 stool samples, 10 vendor salad samples, and 36 water samples. Bivariate analysis was conducted to determine factors associated with cholera and multivariate analysis was used to identify predictors of cholera in Niger State at a significance level of p<0.05. Results: A total of 2,051 cases were reported with a CFR of 6.5%. Wushishi LGA had the highest CFR (40.0%) while Bosso LGA had the highest AR of 127.3/100,000 population. Children aged 0 to 9 years comprised 25.8% (530/2051) accounting for the largest proportion of the affected population. Consumption of water stored in an uncovered wide-mouthed container (AOR: 2.81; 95% CI: 1.36-5.76) and being less than 20 years of age (aOR: 0.34, 95%CI: 0.14-0.82) were independently associated with cholera. Vibrio cholerae was cultured from 47(70.1%) stool, 6(60%) salads, and 14(38.9%) water samples. Conclusion: We confirmed the presence of a cholera outbreak in Niger State with a high CFR. Storing water in uncovered open-mouthed containers and being aged 20 plus years were risk factors. We educated the community on the proper treatment and storage of water.