Climate change influences on the annual onset of Lyme disease in the United States

Lyme disease is the most commonly reported vector-borne illness in the United States. Lyme disease occurrence is highly seasonal and the annual springtime onset of cases is associated with climatic variability. A climate-based empirical model is forced with downscaled climate model simulations to project the impacts of 21st century climate change on the annual onset week of Lyme disease individually and collectively for the 12 states where >90% of cases occur. The average onset week is projected to become earlier nationally by 0.4-0.5 weeks for 2025-2040, and by 0.7-1.9 weeks for 2065-2080 as a result of winter and spring temperature increases, and offset partially by increases in springtime saturation deficit and precipitation. Though many non-climatic factors have the potential to overwhelm the influence of climate change, the results of the present study suggest that future climate change will make environmental conditions more suitable for earlier annual onset of Lyme disease cases in the United States.