Stochastic treatment regimes in climate-health research: Reassessing malaria risk under warming scenarios in Colombia

Malaria remains a significant public health challenge, mainly because climate change is altering transmission dynamics. This study investigates the relationship between rising temperatures and malaria cases across the 100 municipalities in Colombia with the highest incidence from 2007 to 2023. We employed causal machine learning techniques to analyze how incremental temperature impacts malaria incidence while controlling for valid confounding variables. Our findings reveal that with the currently observed temperature, malaria transmission intensifies with temperatures between 15 and approximately 23.5 °C but declines at higher temperatures, indicating an optimal range for transmission. Our results suggest an exposure-response relationship where higher temperature increases are associated with greater reductions in the probability of excess malaria cases. The Average Treatment Effect (ATE) on excess malaria cases for the evaluated temperature regimes showed a progressive decrease, from -0.007 when temperature increased by 0.5°C to -0.063 when temperatures were increased by 2.0°C, relative to current temperatures. These results suggest that further warming could constrain malaria transmission intensity in regions already experiencing high temperatures. This research underscores the importance of tailored public health strategies that consider local temperature profiles and socio-economic conditions in malaria control efforts.Author summary: This study explores the relationship between climate change and malaria transmission in Colombia, focusing on the impact of rising temperatures on malaria incidence. We analyzed data from the 100 municipalities most affected by malaria between 2007 and 2023. Our results indicate that while warmer temperatures can enhance malaria transmission, there is a threshold beyond which transmission declines, revealing a non-linear relationship. Specifically, we found that the Average Treatment Effect on excess malaria cases decreases if future temperatures rise, suggesting that in areas already experiencing high temperatures, further warming may actually reduce transmission risk. These insights highlight the need for targeted interventions that address local climatic and socio-economic factors to effectively manage malaria risk in vulnerable regions.