Mosquitos in two Franklin County towns have tested positive for West Nile virus.
According to notices from the town of Deerfield and the Franklin Regional Council of Governments (FRCOG), mosquito samples collected in Deerfield and Northfield have tested positive. Still, this has not changed the risk level in Franklin County, as the risk of contracting the virus is low, according to the Massachusetts Department of Public Health. Hampshire County’s risk level is also low. Changes to risk levels for low or moderate risk for West Nile virus are updated on Mondays or Thursdays.
Two of the three mosquitos that tested positive were part of a sample collected on July 21 in Northfield and the third tested positive in Deerfield on June 30.
“This is very normal for this time of year,” FRCOG’s Regional Public Health Nurse Meg Ryan said. “The state tracks arbovirus, the West Nile virus and [Eastern Equine Encephalitis].
“The thing with West Nile virus, for most people, it’s not a serious disease,” Ryan added. “It is often like a cold; it can go undetected. But, for a few people, especially immunocompromised people, it can be a serious disease.”
Across the state, only mosquitos have tested positive for West Nile virus thus far, with no animals or humans being infected. In 2025, the state of Massachusetts had 451 mosquitos test positive for the virus.
The typical season for West Nile virus is June to late October, and the peak for humans being diagnosed with it is late August to early September.
There are multiple steps that people can take to avoid contact with mosquitos. These include, but are not limited to, wearing insect repellent when outdoors, wearing long sleeves and long pants from dawn to dusk, and being aware of stagnant water (such as swimming pools, bird baths, etc.) and dumping the water when necessary. Residents are also advised to use mosquito netting on baby carriages and playpens, and repair window screens at their residences.
“If you have a pond, you can use mosquito dunks to prevent the larvae from hatching,” Ryan noted. “It’s very safe.”
In humans, West Nile virus symptoms can range from not presenting at all to severe. According to the U.S. Centers for Disease Control and Prevention, symptoms include fever, headache, body aches, vomiting, diarrhea or rash. The most severe cases can affect the central nervous system and result in hospitalization or death.
Around 2,000 people in America contract West Nile virus annually, however, this number is believed to be lower than the actual number of infections due to many people not showing symptoms or attributing milder symptoms to other causes. About 1,300 of the reported cases are considered severe, with around 130 people dying each year from the virus.
Between 2001 and 2025 in Massachusetts, 273 people were reported as having West Nile virus, with 20 having died, according to the Massachusetts Department of Public Health. Last year, there were nine reported cases of the virus in humans in Massachusetts, with none occurring in Franklin County.
Ryan mentioned that, “as far as I know, West Nile virus [distribution] is pretty even across the state.”
“I just want to emphasize that this is normal. This is public health doing its due diligence and tracking what’s happening,” Ryan continued. “For most people this is not a serious disease, but we should all take precaution to avoid unnecessary exposure.”
