Mosquito-borne Diseases

Mosquito-borne Diseases

Mosquito season in Vermont begins in the spring, but does not typically pose a health risk until the summer months. By July, some mosquitoes may be carrying viruses that cause diseases such as West Nile virus (WNV) infection and Eastern equine encephalitis (EEE).

The Health Department’s Vector-borne Disease Program is responsible for tracking and responding to mosquito-borne diseases. We investigate reported cases of disease, collect and analyze data to detect trends in disease activity, collaborate with other state agencies and work to educate Vermonters about prevention.

Mosquitoes from around the state are collected and tested for evidence of WNV and EEE. The Department tracks this information and updates the mosquito surveillance webpage weekly.

See the weekly surveillance results

The best way to avoid mosquito-borne diseases is to prevent mosquito bites. The Health Department recommends wearing long-sleeved shirts and long pants when outside, limiting time spent outdoors at dawn and dusk when the mosquitoes are most active, and using an insect repellent that has been proven to be safe and effective against mosquitoes.

Travel to other countries can raise the risk of exposure to other mosquito-borne diseases. Check the CDC Travel Health web page to know before you go. 

In This Section

The Health Department summarizes mosquito testing results and reports of human and animal illnesses every week during the summer and early fall, and compiles data each year in an annual surveillance report.


In Vermont mosquito season begins in spring but does not typically pose a health risk until the summer months. Take precautions against mosquito bites to protect yourself from mosquito-borne diseases. 

Eastern equine encephalitis (EEE) is a rare but serious disease caused by a virus and spread by infected mosquitoes. The disease most commonly affects people and horses.

West Nile virus has been has been found in all counties of Vermont and continues to be detected in mosquitoes each year – another reason to take precautions against mosquito bites.

The mosquito that transmits Zika is not known to be present in Vermont. But travelers to Zika-affected countries can be infected, and the virus can be spread during sex with a Zika-infected sex partner.