Hydroclimatic Extremes and Climate Variability as Drivers of Malaria Risk in Sub-Saharan Africa

A changing climate is altering mosquito distributions and transmission seasons, exposing populations with limited acquired immunity to renewed malaria risk. We examined how hydroclimatic extremes and climatic variability influence malaria among children under five, who possess minimal natural immunity, across sub-Saharan Africa over an 18-year period.

 

We analysed malaria outcomes for up to 350,000 children aged 5–59 months from Demographic and Health Surveys (2006–2023) across 26 countries, linking them to high-resolution hydroclimatic exposures. These included the Standardised Precipitation–Evapotranspiration Index (to capture extreme wetness and dryness), air temperature, precipitation, soil moisture, actual evapotranspiration, and specific humidity. Distributed lag non-linear models were used to estimate exposure–lag–response relationships over short to medium lags (≈1–6 months), and to test effect modification by household and behavioural factors such as insecticide-treated net (ITN) use.

 

Extreme wetness was consistently associated with elevated malaria risk, with stronger effects for more intense and prolonged events. Extreme dryness generally reduced or had no effect on risk, though short moderate dry spells showed a slight increase. Precipitation increased risk up to ~120 mm, beyond which excessive rainfall reduced risk, particularly at 1–4-month lags. Soil moisture elevated risk up to ~80 mm before plateauing, while actual evapotranspiration showed a strong, near-linear positive association. In contrast, specific humidity above 14 g/kg was protective. Risk peaked around 24 °C and declined at higher temperatures, mainly at short lags (1–2 months). Elevated risk at cooler temperatures was most evident among children not sleeping under ITNs.

 

Hydroclimatic extremes and short-term climatic anomalies strongly shape malaria risk through their influence on vector dynamics and transmission timing. Understanding these pathways is essential for integrating malaria control and early warning systems into anticipatory action frameworks for hydroclimatic extremes, tailored to local contexts.