Cholera outbreaks in sub-Saharan Africa during 2010-2019: a descriptive analysis

Background: Cholera remains a public health threat, but is inequitably distributed, especially affecting areas without universal access to safe water and sanitation, including much of sub-Saharan Africa. Lack of standardized reporting and inconsistent outbreak definitions limit our understanding of cholera outbreak epidemiology. Methods: We curated a database of cholera incidence and mortality from sub-Saharan Africa from 2010 to 2020 and developed methods to reconstruct epidemic curves. We then described the distribution of key outbreak metrics, including outbreak size and duration. Results: We identified 999 suspected cholera outbreaks in 744 unique regions across 25 sub-Saharan Africa countries, and outbreak periods accounted for 1.8 billion person-months (2% of the total during this period) from January 2010 through January 2020. Among the 692 outbreaks reported from second-level administrative units (e.g., districts), the median attack rate was 0.8 per 1,000 people (IQR, 0.3-2.4 per 1,000), the median epidemic duration was 13 weeks (IQR, 8-19), and the median early outbreak reproductive number was 1.8 (range, 1.1-3.5). Rural outbreaks had more than twice the case fatality risk than urban ones (median of 1.8% versus 0.8%). Larger attack rates were associated with longer times to outbreak peak, longer epidemic durations, and lower case fatality risks. Conclusions: Despite reporting gaps and the limitations of analyzing outbreaks by administrative units, this work provides a baseline from which to monitor progress towards cholera control and essential statistics to inform outbreak management and emergency response in sub-Saharan Africa.