Mosquitoes in two Hampshire County and neighboring communities, including Holyoke, have tested positive for West Nile virus.
The Holyoke Board of Health released an advisory on Thursday stating that a total of 18 mosquitoes testing positive for the virus had been trapped in Hampshire and Hampden counties: one in Northampton, two in South Hadley, three in Holyoke, six in Chicopee and three in West Springfield.
Two communities from Franklin County, Deerfield and Northfield, had mosquito samples test positive for West Nile virus in June and July earlier this year.
The state Department of Public Health (DPH) has a dashboard tracking West Nile virus infection numbers and risk level across the state, showing about half of Hampshire County communities are currently considered to be at a “moderate” risk level, including Northampton, Easthampton, Amherst, South Hadley and more. Moderate risk level is defined as infection has or is likely to occur.
There has been a total of 271 positive mosquito samples statewide this year, and five confirmed human cases. However, the cases were located in Suffolk and Middlesex counties. In 2025, 451 mosquitoes tested positive for the virus statewide.
The typical season for West Nile virus and Eastern Equine Encephalitis is June to late October, and the peak for humans being diagnosed is late August to early September. Mosquitoes are most prevalent at dawn and dusk, and in wooded and swampy areas.
There are multiple steps that people can take to avoid contact with mosquitoes. These include wearing insect repellent when outdoors, wearing long sleeves and long pants from dawn to dusk, and being aware of stagnant water — swimming pools, bird baths and more — 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.
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.
Between 2001 and 2025 in Massachusetts, 273 people were reported as having West Nile virus, with 20 having died, according to the DPH.
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.
For more information, visit the state Department of Public Health website.
