Determinants of mortality among cholera patients treated at urban cholera treatment centers during the widespread cholera outbreak in Kenya, 2022-2023: a retrospective matched case-control study

Cholera outbreaks continue to pose significant public health challenges globally, with Kenya experiencing recurrent episodes. The recent 2022-2023 outbreak underscored notable disparities in mortality rates among cholera cases across different parts of the country. This retrospective matched case-control study aimed to investigate factors contributing to cholera mortality in one of the Kenyan cities. We defined a case as any person who met the suspected or confirmed cholera case definition between October 2022 and October 2023 and died, while controls were those who met the suspected or confirmed clinical cholera case definition in the same period and survived. Cases and controls were identified from patient registers and were matched on age group and date of admission. We identified 38 cases matched to 76 controls from 196 records at two cholera treatment centers (CTCs). The median age was 38 (interquartile range: 27, 51) for the cases and 39 (29, 51) for the controls. The patients below five years were 5% of the cases and 3% of the controls. The proportion of males was 71% of the cases and 67% of the controls. Our study found a high mortality rate at 19% among the 196 records available at the CTCs. Few patients (4%) reported using oral rehydration solution (ORS) at home before admission. At the CTCs, those receiving intravenous rehydration combined with ORS (aOR 0.03 95% CI: 0.00, 0.64) and zinc supplementation (aOR 0.11 95% CI: 0.02, 0.44) had lower odds of dying. Being re-evaluated by a clinician (aOR 0.24 95% CI: 0.06, 0.97) was also identified as protective. The study findings will inform cholera case management training for healthcare workers and support justification for making ORS widely available during outbreaks to prevent cholera-related deaths.