The state Department of Public Health has updated its West Nile virus risk map and increased the risk level for 10 Franklin County towns from low to moderate.
The West Nile virus risk level is now moderate in the towns of Bernardston, Charlemont, Deerfield, Heath, Greenfield, Gill, Leyden, Monroe, Northfield and Rowe. The risk level remains low in the rest of Franklin County.
“WNV findings in mosquitoes have accelerated rapidly over the last several weeks,” state epidemiologist Catherine M. Brown said in a statement. “We are now in the peak time for transmission of mosquito-borne disease to people, and it is important for people to know that so they can take steps to protect themselves.”
The change in risk level came just as the state Department of Public Health announced Tuesday the first human case of West Nile virus in Massachusetts this year, affecting a woman in her 70s who was exposed in Middlesex County.
“West Nile virus can be a very serious disease and its presence in mosquitoes remains high right now in Massachusetts,” Public Health Commissioner Dr. Robert Goldstein said in a statement Tuesday. “While September brings cooler air and the return to school for many in the state, the risk from WNV is going to be elevated for some time. Residents should continue to take precautions to avoid mosquito bites.”
West Nile virus can cause illness ranging from a mild fever and headaches to more serious diseases like encephalitis or meningitis. According to the Pioneer Valley Mosquito Control District, “severe illness is very rare and roughly 80% of people infected with the virus do not develop any symptoms.” Symptoms such as muscle aches, tremors, fatigue and rash typically develop between two and 14 days after being bitten. While it can impact people of all ages, people over the age of 50 are at higher risk of contracting a severe infection.
The State Public Health Laboratory confirmed the first West Nile virus-positive mosquitoes in Massachusetts this year on June 17, and the first positive mosquito sample in Franklin County came on July 15 in Leyden, followed by a positive sample in Deerfield on July 22. To date, there have now been eight positive samples taken across the county.
According to the Department of Public Health’s factsheet on West Nile virus, it was first detected in the United States in 1999. Between 2014 and 2023, 131 people have reportedly been infected with West Nile virus in Massachusetts, resulting in eight deaths.
To protect yourself from the virus, health officials recommend people limit time outdoors during peak mosquito hours (dusk to dawn) and wear long sleeves, pants and insect repellent that contains DEET, permethrin, picaridin, KBR 3023, IR3535 or lemon eucalyptus oil while outside. The Department of Public Health also recommends draining all standing water, which serves as a breeding ground for mosquitoes, and installing screens on windows and doors to prevent mosquitoes from coming inside.
Additionally, there have been 18 Eastern equine encephalitis (EEE)-positive mosquito samples and no human or animal cases so far this year.
For more information about West Nile virus, visit mass.gov/info-details/west-nile-virus-wnv.
