Residents are encouraged to take precautions when outdoors, as West Nile virus has now been detected in mosquitos in five Franklin County communities.
According to the state Department of Public Health, no human cases of West Nile have been reported in Franklin County; however, two human cases were found in Middlesex County in eastern Massachusetts. Meanwhile, mosquito samples have tested positive for West Nile virus in Greenfield, Erving, Montague, Northfield and Deerfield.
Greenfield, in a post on the city website, advised the public on Tuesday that West Nile virus had been detected in two mosquitos from two separate samples in the city.
“The city’s Health Department continues to monitor the situation and increased surveillance is being conducted,” the notice advises.
The town of Erving similarly shared guidance on its town website on Tuesday after announcing that West Nile virus had been found in mosquitos collected from Erving. The town likewise had one West Nile virus-positive mosquito sample identified in 2025.
According to the Department of Public Health’s Bureau of Infectious Disease and Laboratory Sciences, the positive mosquito samples were found in Montague on Aug. 5, Greenfield on Aug. 12 and Erving on Aug. 19.
The Department of Public Health has raised the risk level for the virus in those five communities to moderate, while the rest of the county remains at low risk. To avoid infection, people are encouraged to use mosquito repellent, wear long clothing, avoid going outdoors during peak mosquito activity hours and remove stagnant water on their properties to prevent mosquito breeding.
“We are currently in peak season for WNV in mosquitos, and the risk for many across Massachusetts is high,” Public Health Commissioner Dr. Robert Goldstein said in a statement. “Those who are older or have compromised immune systems are especially at risk. I want to remind everyone to continue to use repellent, cover up with clothing when the weather permits, consider moving indoors during dusk to dawn hours when mosquitos are biting, and make sure to empty anything that may be collecting water outside your home.”
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. Last year, there were nine reported cases of the virus in humans in Massachusetts, with none occurring in Franklin County. In 2025, the state had 451 mosquitos test positive for the virus, and Franklin County had 16 reported cases of the virus in mosquitos.
For more information, visit the Department of Public Health’s website.