Cholera case trends in Eastern Africa using surveillance data, 2007-2024

Abstract

Introduction

Cholera is a public health threat in Africa, with an estimated 68,480 cases and 895 deaths reported across seven of 14 Member States in the Eastern region in 2023. Within the region, cholera outbreak has been protracted in the horn of Africa, with countries responding to the outbreak amid prolonged harsh drought, floods and complex humanitarian emergencies. In recent months, an upsurge in cases and deaths has been observed in the region, with five countries reporting active outbreaks this year. We describe the trend of cholera cases in Comoros, Ethiopia, Kenya, Somalia and Tanzania for 2007-2024.

Methods

Descriptive trend analysis of cholera case data for Comoros, Ethiopia, Kenya, Somalia and Tanzania, from 2007-2024, was performed. Data were obtained from the Event Management System of the Africa Centres for Disease Control and Prevention (2023-2024) and the Global Infectious Disease and Epidemiology Network (GIDEON) online resource for data (2007-2022). Water, Sanitation and Hygiene (WASH) data was sourced from WHO/UNICEF Joint Monitoring Program for WASH. The term 'cholera case' includes both confirmed and suspected.

Results

From 2007 to 5 April 2024, a total of 578,449 cholera cases and 8,514 deaths [case fatality rate (CFR): 1.5%] were reported from Comoros, Ethiopia, Kenya, Somalia and Tanzania. Somalia accounted for 55.2% (315,972) of the cases and 54.6% (4,700) of the corresponding deaths. The average CFR per year was 1.4%, ranging from 0.3% in 2014 to 2.4% in 2016. During the review period, notable geographical patterns that were triggered by climate change were observed. Somalia experienced annual cholera outbreaks beginning November and December and receding in May, with largest occurrences in 2011 (77,636 cases) and 2017 (75,414 cases). Widespread outbreaks occurred in Ethiopia from 2007-2010, with a high peak in 2009 (31,509 cases) and recently in 2023 (29,869 cases). For this year, cases in Kenya appear to be on the decline while Tanzania shows an increasing pattern. Comoros reported its first cholera outbreak since 2007 in February 2024 through a cross-border event with Tanzania. Ethiopia is among countries in Africa with the largest population practicing open defecation in 2022.

Discussion

The trend analysis underscores the persistent nature of cholera outbreak in the Eastern region. Climate change impacts the dynamics of the outbreak by limiting access to safe water and sanitation, and triggering increased cross-border movements. The average CFR per year surpassed the recommended <1% threshold.

Conclusion

The cholera response requires a regional multi-sectoral and coordination mechanism approach, given the same protracted nature and cross-border transmissions. Significant resources are needed to implement long-term WASH strategies. With the predicted above-normal rainfall for the horn of Africa between March and May 2024, climate change in relation to health outcomes should be considered an emerging area of focus.