The Role of Climate Change in the Expansion of Dengue

Climate change-related weather and extreme events are increasing in intensity and frequency, affecting infectious disease transmission globally. Dengue, a climate-sensitive vector-borne disease, to which over half the world's population is at risk of infection, has expanded its geographical range over recent decades. The 2023/24 season marked the largest ever dengue outbreak year in the Americas, coinciding with the hottest year on record in the Americas. Here, we use statistical models to investigate the Brazil 2023/24 dengue season and attribute how anthropogenic climate change impacted it. We analyze >20 years of dengue data across >5000 municipalities and find that observed temperature anomalies in municipalities of southern Brazil pushed those locations into optimal thermal conditions for dengue transmission. In contrast, in northern Brazil, 2023/24 temperatures became too high for effective transmission, resulting in lower dengue incidence compared to a counterfactual scenario without anthropogenic climate change. We test the generalizability of our model to high altitude areas in Mexico, where dengue has been expanding. Our work empirically demonstrates how a climate-change-related temperature anomaly led to the range expansion and growth of dengue across variable ecological and socio-economic settings, with implications for preparedness, adaptation, mitigation, and resilience planning.