Retrospective Analysis of Cholera/Acute Watery Diarrhea Outbreaks in Ethiopia From 2001 To 2023: Incidence, Case Fatality Rate, and Seasonal and Multiyear Epidemic Patterns

Abstract

Background: The Ethiopian government has developed the multisectoral cholera elimination plan (NCP) with an aim of reducing cholera incidence and case fatality rate (CFR). To better understand and monitor the progress of this plan, a comprehensive review of national cholera epidemiology is needed.

Methods: Reported data on cholera/acute watery diarrhea (AWD) cases in the past 20 years were extracted from the Ethiopian Public Health Institute and World Health Organization databases. Descriptive statistics, Pearson χ2, and logistic regression analyses were conducted.

Results: From January 2001 to November 2023, a total of 215 205 cholera/AWD cases, 2355 deaths with a cumulative CFR of 1.10% (95% confidence interval [CI], 1.092-1.095), and a mean annual incidence rate of 8.9/100 000 (95% CI, 6.5-11.3) were reported. Two major upsurges of cholera epidemics were found in the last two decades with mean attack rate (AR) of 20.57/100 000 in 2006-2010 and 14.83/100 000 in 2016-2020. Another resurgence of outbreaks occured in 2021-2023 (mean AR, 8.63/100 000). In 2015-2023, 54.0% (53 990/99 945) of cases were aged 15-44 years. National cholera CFR (3.13% [95% CI: 2.1-4.5]) was the highest in 2022. The 2015-2023 cumulative cholera CFR was different across regions: Benishangul Gumuz (6.07%), Gambela (1.89%), Sidama (1.42%), Southern Nation, Nationalities, and Peoples' (1.34%), Oromia (1.10%), and Amhara (1.09%). Cholera/AWD patients in older adults (≥45 years), severe dehydration, peak rainy season (June-August), and outpatients were associated with higher risk of death.

Conclusions: Cholera has been a public health problem in Ethiopia with case fatalities still above the global target. Case management needs to be improved particularly in outpatients and older populations. Outbreak preparedness should be rolled out well in advance of the typical rainy seasons. Significant investments are essential to advance the cholera surveillance system at healthcare setting and community level. Underlying factors of cholera deaths per areas should be further investigated to guide appropriate interventions to meet the NCP target by 2028.

Keywords: Ethiopia; case fatality rate; cholera; incidence; seasonality.

Figure 1.

Cholera epidemic curves and seasonal patterns in Ethiopia. A, Successive cholera epidemic waves in Ethiopia every year from 2015 to 2023. The presented epi-weeks exhibit the magnitude and persistence of cholera outbreaks in the country. B, Seasonal pattern of cumulative cholera case counts reported by the major seasons in Ethiopia from 2015 to 2023.

Figure 2.

Cholera epidemic curves per region and years in Ethiopia. Graphs show the distributions of cholera cases per year and epi-weeks in each region of Ethiopia during 2015–2023. Abbreviation: SNNPR, Southern Nation, Nationalities, and Peoples’ Region.

Figure 3.

Annual and mean cholera incidence in Ethiopia. A, Annual trends of cholera incidence per 100 000 population in Ethiopia during 2015–2023. B, Trend of mean cholera incidence per 5-year period during 2001–2023 in Ethiopia. Abbreviation: AR, attack rate.

Figure 4.

Annual and mean cholera case fatality rate in Ethiopia. A, Annual trends of cholera case fatality rate (CFR) in Ethiopia during 2015–2023. R² is the coefficient of determination and the best trendline determined using Expon. (CFR [%], exponential trendline). B, Trend of mean cholera CFR per 5-year period during 2001–2023 in Ethiopia.