Extreme rainfall, flooding and malaria in the Sahara: outbreak analysis in Kidal, Mali 2024

Extreme rainfall caused severe flooding in Kidal, northern Mali, in 2024, raising concerns about the outbreak of malaria associated with climate change. The objective of this study was to describe this epidemic and the response implemented by national and regional authorities.

A historical cohort study was conducted in the Kidal region, covering the entire population. Weekly malaria case data recorded by the national health system between May 2024 and February 2025 were analyzed in conjunction with precipitation data from the Tropical Rainfall Measuring Mission (TRMM, spatial resolution: 0.25°). The interventions included seasonal malaria chemoprevention (SMC), extended to children under 15 years of age, and deployment of mobile health teams in remote areas. The effect of these interventions on malaria cases per 1000 person-weeks was estimated using Generalized Additive models (GAM) applied to interrupted time series, taking rainfall into account. In addition, the spatial distribution of the population at risk was estimated using WorldPop population data.

Rainfall began in week 25 and continued for 15 weeks. The malaria epidemic began in week 30, peaked in week 39 with 1,014 cases, and lasted for 28 weeks, with 1.688 (95% CI 1.687-1.690) cases per 1000 person-weeks. Incidence was highest among children under five. The interventions implemented, using extended SMC and mobile health teams, led respectively to a significant reduction in morbidity (respective Standardized Incidence Ratios (SIRs) of 0.50; 95% CI 0.33-0.75 and SIRs = 0.48; 95% CI 0.28-0.82).

Malaria outbreaks associated with flooding are becoming increasingly frequent in the context of extreme weather conditions. These situations pose a major challenge for malaria control programs and highlight the need to strengthen surveillance systems. The implementation of weather-based preparedness strategies is essential, including expanding preventive treatment coverage (SMC), deploying mobile health teams, and pre-positioning essential inputs.