Vector-borne diseases (VBD) are infectious diseases that are transmitted to humans by animals, also called "vectors", such as mosquitoes, ticks, and rodents. Climate change can cause vectors or the diseases they carry to spread more rapidly and to new areas, putting people at risk.
How does climate change affect vector-borne disease?
Changes in temperature and humidity can affect where vectors live, and may affect the life-cycles of the pathogens they carry. For example:
- Drought and heat
- West Nile virus activity often appears to be greatest during La Nina conditions of drought and hot summer temperatures.
- Wet conditions
- A prolonged rainy season could make California more at risk for the introduction and establishment of exotic vectors, such as those that carry dengue and yellow fever.
A changing climate will allow vectors to exist where they previously did not.
How do vector-borne diseases impact health?
Climate change may make the environment more favorable for Human Hantavirus Cardiopulmonary Syndrome (HCPS), Lyme disease, and West Nile Virus (WNV). This may place humans at greater risk for these diseases. For example:
- Human Hantavirus Cardiopulmonary Syndrome
- HCPS infections have remained rare in California, but more frequent flooding or heavy precipitation cycles could increase deer mice populations, which act as carriers for hantavirus. People at risk for infection include those exposed to rodent-infested dwellings, such as poorly maintained or long-vacant cabins in areas with large deer mice populations.
- Lyme Disease
- Climate change may increase the distribution of ticks capable of transmitting Lyme disease, especially in areas that receive more moisture.
- West Nile Virus
- Higher temperatures and rainfall may increase mosquito populations that carry WNV. Research has shown that drought conditions may also cause spikes in some mosquito populations due to disruptions in aquatic food-webs, while also driving closer contact between mosquitoes and birds at dwindling watering holes.
The need for vector management may also cause indirect health effects. Pesticides may be used in response to disease vectors. Human exposures to pesticides may cause a wide variety of health effects, depending on the pesticide used and the amount of exposure.