Extreme precipitation, exacerbated by anthropogenic climate change, drove Peru's record-breaking 2023 dengue outbreak

HighlightsO_LIIn March 2023, Cyclone Yaku was followed by a large dengue epidemic in northwest Peru C_LIO_LIExtreme precipitation during Cyclone Yaku caused 60% of dengue cases C_LIO_LIMore cyclone-attributable cases occurred in warm, urban, flood-susceptible districts C_LIO_LIGlobal warming has increased the risk of warm, very wet March weather in the region C_LI Science for SocietyAnthropogenic climate change is increasing the risk of extreme weather that can lead to infectious disease epidemics, but few studies have directly measured this health consequence of climate change. Extreme precipitation can drive outbreaks of mosquito-borne diseases by displacing people, disrupting public health activities, and creating aquatic breeding habitat. Here, we quantify the effects of extreme precipitation during Cyclone Yaku in northwestern Peru in March 2023. The cyclone was immediately followed by a dengue outbreak where cases exceeded historic averages by tenfold. We estimate that 60% of cases (or 22,014 cases) reported over three months in the affected districts were attributable to extreme precipitation during Cyclone Yaku. Compared with the preindustrial era, extremely wet March conditions were 31% more likely to occur (and 189% more likely to co-occur with warm temperatures suitable for dengue transmission) in recent decades in northwestern Peru. Assessing the linkages between climate change, extreme weather, and outbreaks of dengue and other infectious diseases is crucial for understanding the current impacts of climate change and for preparing for future health risks. eTOC SummaryThis study examines relationships between historical climate forcing, extreme weather, and health, focusing on Cyclone Yaku and Perus 2023 dengue epidemic. Historical climate forcing has increased the likelihood of extreme precipitation coinciding with warm temperatures suitable for transmission in March in northwest Peru. In turn, extreme precipitation during Cyclone Yaku caused a majority of dengue cases in the epidemic, especially across warmer districts. Extreme weather, made more likely by climate change, is already having an impact on human health. Climate change is increasing the likelihood of extreme weather that can drive outbreaks of climate-sensitive diseases. For example, dengue burden has recently increased rapidly with unusually warm and wet conditions. However, linkages between historical climate change, extreme weather, and mosquito-borne disease have not been traced quantitatively. Here, we analyze the contribution of extreme precipitation to dengue in northwestern Peru during Cyclone Yaku in March 2023. Using generalized synthetic control methods, we estimate 60% of cases were attributable to extreme precipitation and more cyclone-attributable dengue cases occurred in warmer, more flood susceptible, and more urban districts. Historical climate forcing has increased the likelihood of concurrent extreme precipitation and warm temperatures suitable for dengue transmission in northwestern Peru in March by 189%. This case study is one of the first to estimate cases of mosquito-borne illness caused by extreme weather conditions and shows those conditions were made more likely by climate change.