Mosquitoes Test Positive for Eastern Equine Encephalitis Virus in Grand Isle and Franklin Counties

People should protect themselves against mosquito bites to prevent spread of disease

WATERBURY, VT – Health officials are urging people to take steps to prevent mosquito bites after mosquitoes from Grand Isle and Franklin counties tested positive for Eastern equine encephalitis (EEE) virus — a serious and potentially fatal mosquito-transmitted infection.

This is the first detection of EEE virus in the 2024 mosquito testing season in Vermont.

The Vermont Agency of Agriculture, Food & Markets collects mosquitoes at locations throughout the state for testing at the Department of Health Laboratory. So far this season, nearly 18,000 mosquitoes have been tested. The positive EEE virus samples were collected on July 22 from Alburgh and Swanton. West Nile virus has also been detected in mosquitoes in several towns this year.

There have been no human cases of EEE or West Nile in Vermont this year. The most recent confirmed cases of EEE were in two people in 2012, both of whom died.

The risk for EEE infection is highest from late summer into fall. Most people infected with EEE virus will have no or mild symptoms, such as fever, chills, fatigue, and joint and body aches. While rare, EEE can result in severe disease, including encephalitis, an inflammation of the brain. EEE is fatal in about one-third of people who develop severe disease. Many who recover from severe EEE disease are left with disabilities.

Anyone with symptoms of EEE should contact their health care provider as soon as they start to feel sick.

“Finding EEE virus in mosquitoes is a warning sign that people in these areas could be at risk for this potentially deadly disease,” said Health Commissioner Mark Levine, MD. “Please take steps to protect yourself and your family from mosquito bites as you enjoy the rest of your summer.”

Protect Yourself and Your Family by Preventing Mosquito Bites

Preventing mosquito bites is the best way to protect against EEE and West Nile disease. There is no specific treatment or human vaccine for EEE. The Health Department offers these simple and effective tips:

• Wear long-sleeved shirts and pants when outdoors.
• Limit your time outside at dawn and dusk when mosquitoes are more likely to bite.
• Use insect repellent labelled as effective against mosquitoes. The EPA has a tool to help find the right repellent for you. These repellants can also protect you from tick bites. 
• Get rid of standing water in places like gutters, tires, play pools, flowerpots, and bird baths. Mosquitoes breed in water that has been standing for more than four days.
• Cover strollers and outdoor playpens with mosquito netting.
• Fix holes in screens and make sure they are tightly attached to doors and windows.

Recommendations for Horse Owners

Horse owners should consult their veterinarians and make sure their animals are up to date on vaccinations for EEE, West Nile and other viruses spread by infected insects or ticks. Horses cannot spread EEE or West Nile viruses to humans or other horses, but the viruses can cause neurologic disease and death in unvaccinated animals. In 2023, an unvaccinated Vermont horse died from the virus.

For more information:

Eastern Equine Encephalitis (Health Department)
West Nile Virus (Health Department)
Mosquito Bite Prevention (Health Department)
Mosquitoes in Vermont (Agency of Agriculture)
Mosquito Surveillance in Vermont (Agency of Agriculture)