The incidence of vector-borne and zoonotic diseases (VBZD) is difficult to predict and model. Climate is one of many variables known to affect the rates of these infectious diseases. Climate change may result in changing distribution of VBZD prevalent in the U.S. This could cause formerly-prevalent diseases such as malaria and dengue fever to re-emerge, or facilitate the introduction and spread of new disease agents, such as West Nile virus. At this time, scientists do not have the understanding of disease ecology in each instance needed to make predictions.
The potential for climate change to impact the range and incidence of VBZD in the U.S. rests with climatic influences on the ecology of insect vectors and animal hosts, and on the life cycles of the disease-causing germs they carry. For instance, as temperature increases, the malaria parasite reproduces at a higher rate, and mosquitoes take blood meals more frequently, up to a certain ceiling determined by individual species.
Some VBZD agents prevalent in the U.S., including Lyme disease and Hantivirus, show evidence of seasonality Current evidence suggests that the range of these diseases could change with a changing climate. Nevertheless, our current understanding of the complex transmission cycles of these diseases, along with incomplete understanding of the ecology of insect vectors and animal hosts, and the lack of long-term historical datasets linking weather with VBZD outcomes, makes projections very difficult for VBZD currently prevalent in the U.S.
Long-term research on weather and climate effects on VBZD, including variables not related to climate, such as population dynamics, preventive activities, land use changes, trade and travel, civil unrest, water availability, and other issues, are needed for more confident projections of climate change’s effects on VBZD. Effective prevention and control strategies are known for the majority of these diseases, and such research would greatly increase the effectiveness of early warning systems and other public health strategies for preventing epidemic disease.