Extreme weather events and vector-borne diseases: Quantifying the epidemiological effect of Hurricane Julia on malaria transmission in Colombia

Extreme climatic events, such as hurricanes, are known drivers of vector-borne disease outbreaks; however, quantifying their causal effect remains challenging due to complex spatio-temporal dynamics and unobserved confounders. This study estimates the causal effect of Hurricane Julia (October 2022) on malaria cases in Colombian municipalities. We employed a Generalized Synthetic Control (GSC) framework using the fect package in R to estimate the Average Treatment Effect on the Treated (ATT) and the Conditional Average Treatment Effect on the Treated (CATT). Data were obtained from the national public health surveillance system (SIVIGILA) for the period 2013-2023, along with several climatic, environmental, and socio-economic sources. Our results indicate that the hurricane did not have a clear effect on the ATT. Nonetheless, it shows an uptick in malaria transmission after the event, especially when considering forest coverage in the CATT. The results suggest that the disruption caused by the hurricane intensified transmission cycles, particularly in regions with pre-existing socio-ecological vulnerabilities. These results reveal the need for climate-resilient public health strategies and the integration of extreme weather events into early warning systems for malaria control.