A protracted cholera outbreak in Nairobi City County associated with mass gathering events, Kenya, 2017

Cholera continues to cause many outbreaks in low and middle-income countries due to inadequate water, sanitation, and hygiene services. We describe a protracted cholera outbreak in Nairobi City County (NCC), Kenya in 2017. We reviewed the cholera outbreak line lists from NCC in 2017 to determine its extent and factors associated with death. A suspected case of cholera was any person aged >2 years old who had acute watery diarrhea, nausea, or vomiting, whereas a confirmed case was where Vibrio cholerae was isolated from the stool specimen. We summarized cases using for continuous variables and proportions for categorical variables. Associations between admission status, sex, age, residence, time to care seeking, and outbreak settings; and cholera associated deaths were assessed using odds ratio (OR) with 95% confidence interval (CI). Of the 2,737 cholera cases reported, we analyzed 2,347 (85.7%) cases including 1,364 (58.1%) outpatients, 1,724 (73.5%) not associated with mass gathering events (MGEs), 1,356 (57.8%) male and 2,202 (93.8%) aged [≥]5 years, and 35 deaths (case fatality rate: 1.5%). Cases were reported from all the Sub Counties of NCC with an overall county attack rate of 50 per 100,000 people. Vibrio cholerae Ogawa serotype was isolated from 78 (34.8%) of the 224 specimens tested and all isolates were sensitive to tetracycline and levofloxacin but resistant to amikacin. The odds of cholera-related deaths was lower among outpatient cases (aOR: 0.35; [95% CI: 0.17-0.72]), age [≥]5 years old (aOR: 0.21 [95% CI: 0.09-0.55]), and MGEs (aOR: 0.26 [95% CI: 0.07-0.91]) while threefold higher odds among male (aOR: 3.04 [95% CI: 1.30-7.13]). NCC experienced a protracted and widespread cholera outbreak with a high case fatality rate in 2017. Author SummaryCholera outbreaks are common in Kenya. The highest number of cases were reported in 2015 with 10,536 cases across the country. The subsequent three years also recorded a high number of cholera cases with 6,137 cases in 2016, 4,217 cases in 2017, and 5,638 cases in 2018. During the four years (2015-2018), NCC contributed less than 20.0% of the cholera cases, except in 2017 when the county reported 56.9% (2,737) of the cases. In this study, we sought to describe the burden of cholera in NCC during the 2017 outbreak. We reviewed the cholera outbreak data from NCC in 2017 to determine its extent and risk factors for cholera-related deaths. The findings depict a prolonged and widespread cholera outbreak with the likelihood of death higher among male cases but lower among outpatients, cases aged [≥]5 years old, and cases from the MGEs. More studies on the factors associated with cholera-related deaths are necessary to inform public health response.