Cholera trends in the WHO African region and temporal co-occurrence with El Niño, tropical cyclones, floods and droughts: 2022–2023
Otim Ramadan, Adebola Tolulope Olayinka, Felix Sanni, Susan Nyawade, Olaolu Moses Aderinola, Olushayo Oluseun Olu, Rashidatu Kamara, Tendai Makamure, John Masina, Fred Dratibi, Deborah Barasa, Charles Okot, Ishata Nannie Conteh, Mory Keita, Joseph Okeibunor, Dick Damas Chamla, Fiona Braka, Abdou Salam Gueye, Chikwe IhekweazuIntroduction
Cholera is an indicator of inequity and lack of social development and it majorly affects poor and vulnerable people. Cholera outbreaks linked to seasonality continue to occur unabated in Africa, necessitating better understanding of the disease trends. This study describes the trend of cholera outbreaks in the AFRO region between January 2022 and December 2023 and examines the temporal co-occurrence with major climatic events at the period.
Method
We undertook a descriptive ecological trend analysis of secondary surveillance data on cholera and overlaid outbreak trends with the timing of major climate events from 1 January 2022 to 31 December 2023 from affected countries in the AFRO region. Negative binomial regression with country fixed effects and seasonal harmonics was used to quantify the association between climate event exposure and weekly cholera incidence.
Results
Cumulative cases and deaths reported in 2022 were 90 227 and 2296, with case fatality ratio (CFR) of 2.55% across nine countries. In 2023, a total of 197 132 cases and 2830 deaths (CFR 1.4%) were reported from 17 countries, with the number of affected countries nearly doubling. Population-adjusted attack rates increased from 13.5 per 100 000 in 2022 to 21.9 per 100 000 in 2023. Climatic events ranging from droughts, excessive rainfall, floods and tropical cyclones occurred at different times across the 2-year study period. Negative binomial regression showed that cyclone (incidence rate ratio (IRR) 3.88, 95% CI 2.57 to 5.85), flood (IRR 1.93, 95% CI 1.46 to 2.54) and drought exposures (IRR 3.89, 95% CI 2.93 to 5.16) were each independently associated with higher cholera incidence (all p<0.001).
Conclusion
The seasonality of cholera outbreaks and climatic events continue to be a challenge for countries to deal with. Between 2022 and 2023 in the African region, extreme weather events overlapped with waves of cholera epidemics. It is important to integrate preparedness for cholera and control into contingency planning for climatic events.