Lyme disease is the most common vector-borne disease in temperate zones and a growing public health threat in the US. Tick life cycles and disease transmission are highly sensitive to climatic conditions but determining the impact of climate change on Lyme disease burden has been challenging due to the complex ecology of the disease and the presence of multiple, interacting drivers of transmission. We estimated the impact of prior temperature and precipitation conditions on US Lyme disease incidence and predicted the effect of future climate change on disease. We incorporated 17 years of annual, county-level Lyme disease case data in a panel data statistical modeling approach to investigate prior effects of climate change on disease while controlling for other putative drivers. We then used these climate-disease relationships to forecast Lyme disease cases using CMIP5 global climate models and two potential climate scenarios (RCP 4.5 and RCP 8.5).
Results/Conclusions:
We find that climate is a key driver of Lyme disease incidence across the US, but the relevant climate variables and their effect sizes vary strongly between regions, with larger effects apparent in the Northeast and Midwest where Lyme disease incidence has recently increased most substantially. In both of these regions, key climate predictors included winter temperatures, spring precipitation, dry summer weather, and temperature variability. Further, we predict that total US Lyme disease incidence will increase significantly by 2100 under a moderate emissions scenario, with nearly all of the additional cases occurring in the Northeast and Midwest. Our results demonstrate a regionally-variable and nuanced relationship between climate change and Lyme disease and highlight the need for improved preparedness and public health interventions in endemic regions to minimize the impact of further climate change-induced increases in Lyme disease burden.