Malaria–climate interface in the Pacific and Andean regions of Colombia between 2014 and 2023

Background In Colombia and elsewhere, malaria transmission is highly sensitive to climate. The Standardized Precipitation-Evapotranspiration Index (SPEI) is used in agriculture to schedule crop planting and harvesting. The distribution and spread of malaria vectors are influenced by climatic factors, including humidity, temperature, and precipitation. The occurrence and distribution of water sources influence mosquito reproduction and transmission capacity, as well as human exposure to infectious vectors. This study evaluates the association between i) transmission of Plasmodium falciparum and vivax , represented by the time-varying effective reproductive number ( R _t ), and ii) climate variables — specifically SPEI and temperature — in Colombia from 2014 to 2023. Methods Malaria surveillance data from the Colombian Public Health Surveillance System (SIVIGILA) were analyzed alongside climate data for four malaria-endemic administrative units (departments): Antioquia, Cauca, Chocó and Nariño. R _t was estimated by Plasmodium species using a mechanistic framework informed by regional vector ecology and parasite dynamics. Associations between R _t and climate variables, including lagged effects (1–3 months), were assessed using generalized additive models (GAMs). Results A total of 476,810 malaria cases were reported from 2014 to 2023, with 63.2% due to P. falciparum and 36.8% to P. vivax. In Chocó, generalized additive models showed a strong positive association with temperature. Together with R _t , temperature explained 45.6% of the deviance for P. falciparum in Chocó (R² = 0.381, p < 0.001). In Antioquia, lower SPEI values (drier conditions) were associated with increased transmission, explaining 49.6% of the deviance for P. vivax (p < 0.01). In Nariño and Cauca, temperature was associated with P. falciparum incidence , explaining 45%-50% of the deviance (p < 0.01). R _t values often rose 1–3 months prior to increases in malaria incidence. Conclusions Temperature was moderately associated with malaria transmission in the study area, particularly the Colombian Pacific Coast, specifically for P. falciparum , while both temperature and SPEI were associated with transmission of both Plasmodium species in Antioquia. These findings support integrating climate-informed surveillance indicators to enhance public health preparedness.