Mosquitoes in Vermont's Charlotte Test Positive for Jamestown Canyon Virus Again

A Familiar Threat Returns Earlier Than Expected

The Vermont Department of Health has confirmed that Jamestown Canyon Virus has been detected in northwestern Vermont for the first time. Mosquitoes collected in Charlotte, in Chittenden County, between June 14 and 20 tested positive for the virus. This marks the first detection of a mosquito-borne virus in Vermont this year, and no cases of mosquito-borne illnesses have been reported in people or animals yet this season.

State public health veterinarian Natalie Kwit noted, "It's not too early to take precautions to protect yourself from mosquito bites," adding that "this is a relatively early detection of a mosquito-borne virus in Vermont compared to recent years, but is not abnormal for this virus. We can expect to see more virus detections as the season progresses and the risk of exposure to infected mosquitoes increases."

Vermont's Growing History With This Virus

It was only in 2025 that the Vermont Department of Health began monitoring mosquito populations for Jamestown Canyon virus. That first year of testing turned up positive results among mosquito pools in Marshfield, Rutland, and Whitingham, along with one human case in Windsor County. That human case was confirmed on September 8 in a person from Windsor County through laboratory testing and reporting by their health care provider.

The virus is spread to humans through mosquito bites. Jamestown Canyon virus circulates in the environment between mosquitoes and animals, typically deer. Infected mosquitoes can then spread the virus to people and other animals by biting them. People are considered "dead-end" hosts, meaning they do not spread the virus — even when they are sick — to mosquitoes that bite them. In other words, you can't catch it from a sick neighbor.

What the Virus Can Do — and Why It Matters

Most people with Jamestown Canyon virus don't develop symptoms at all. Some may experience flu-like symptoms a few days to two weeks after a mosquito bite. Initial symptoms can include fever, fatigue, and headache. Some people also have respiratory symptoms such as cough, sore throat, or runny nose. In more serious cases, the virus can cause severe disease, including inflammation of the brain (encephalitis) or the membranes around the brain and spinal cord (meningitis).

About half of patients reported with Jamestown Canyon are hospitalized, though deaths associated with the virus are rare. People who have weak immune systems or who are older may be more likely to develop severe disease. No vaccines or medicines are available to prevent or treat Jamestown Canyon virus disease. Rest, fluids, and over-the-counter pain medications may relieve some symptoms, and in severe cases, patients may need to be hospitalized to receive supportive treatment such as intravenous fluids, pain medication, and nursing care.

What Residents Should Do Right Now

Charlotte's town administrator sent a message to residents urging them to wear long-sleeved clothing when outdoors, use insect repellent, and avoid being outdoors near dawn or dusk. Health officials are also encouraging Vermonters to protect themselves from mosquito bites and the potentially dangerous diseases they can spread, including Jamestown Canyon virus, West Nile virus, and Eastern equine encephalitis (EEE) virus.

The detection in Charlotte is a signal that Vermont's mosquito season is well underway — and that it's showing up in new corners of the state. Jamestown Canyon virus is found throughout much of the United States, but most cases are reported from the upper Midwest, and cases occur from late spring through mid-fall. With Vermont now firmly in the monitoring business and two consecutive years of detections, public health officials are building a clearer picture of just how present this virus is — and residents would be wise to take simple precautions seriously before the season peaks.