Drivers of Malaria Resurgence in Ethiopia (2020–2024): A Bayesian Spatiotemporal Analysis

Background: Following years of progress, malaria has resurged in Ethiopia, threatening national elimination goals. The interacting climatic, biological, and socio-political drivers of the resurgence remain poorly understood. We quantified associations between monthly malaria incidence in Ethiopia from 2020 to 2024 and selected environmental, demographic, vector, and programme factors, and estimated their contribution to the cumulative resurgence during this period.

Methods: We conducted a nationwide analysis of routine surveillance data from 3,593 health facilities across 643 woredas between January 2020 and December 2024, combined with environmental, demographic, vector, and programme datasets. Monthly woreda-level incidence of Plasmodium falciparum and Plasmodium vivax was modelled using a Bayesian spatiotemporal framework.

Findings: P. falciparum cases increased from 0·84 million in 2020 to 4·01 million in 2024, while P. vivax cases rose from 0·27 million to 1·87 million. Higher lagged enhanced vegetation index was associated with higher incidence of P. falciparum (incidence rate ratio [IRR] 1·17, 95% credible interval [CrI] 1·14–1·21) and P. vivax (1·18, 1·14–1·22). Lagged rainfall was also positively associated with P. falciparum (IRR 1·06, 95% CrI 1·04–1·08) and P. vivax (1·05, 1·03–1·07) incidence. Higher lagged minimum and maximum temperatures were associated with higher incidence for both species. Internal displacement was associated with higher P. falciparum incidence (IRR 1·04, 95% CrI 1·02–1·07) but not with P. vivax incidence (1·00, 0·97–1·02). Vector control indicators reflected targeted deployment rather than causal protection. In counterfactual analyses, all examined time-varying drivers jointly accounted for 8·8% (95% CrI 6·3–11·6) of the cumulative modelled increase in P. falciparum and 3·9% (1·5–6·1) of the increase in P. vivax during 2022–2024.

Interpretation: Ethiopia’s malaria resurgence was associated with greater ecological suitability and population displacement in a highly heterogeneous transmission landscape. Ecological factors contributed to the resurgence of both species, whereas displacement was more clearly associated with P. falciparum. However, the time-varying drivers examined explained only a modest proportion of the cumulative increase, suggesting that   residual spatiotemporal processes, health-system disruption, last-mile delivery gaps, intervention effectiveness, evolving parasite and vector biology, mobility and reporting dynamics probably contributed substantially. The findings support proactive, geographically targeted control with enhanced surveillance and tailored interventions for hotspots and mobile or displaced populations.