State public health officials announce first West Nile virus-positive mosquito sample in 2025

On June 17, the Massachusetts Department of Public Health (DPH) announced that West Nile virus (WNV) has been detected in mosquitoes in Massachusetts for the first time this year. The presence of WNV was confirmed by the Massachusetts State Public Health Laboratory in a mosquito sample collected on June 13 in the town of Shrewsbury in Worcester County.

WNV is usually transmitted to humans through the bite of an infected mosquito. While most people do not get sick from WNV, people over the age of 60 and those with certain chronic medical conditions are more likely to develop severe illness.  

Right now the WSN risk in Massachusetts is low. No human or animal cases of WNV have been detected so far this year. In 2024, there were 19 human cases of WNV.

Avoid Mosquito Bites

Health officials urge residents to start using mosquito repellent when outdoors and other measures to avoid mosquito bites to reduce their risk of WNV. This includes:

• Being aware of peak mosquito hours (dusk to dawn).  
• Wearing long sleeves, long pants, and socks when outdoors to keep mosquitoes away from your skin.
• Mosquito-proof your home by draining standing water and using tight-fitting screens in windows and doors.

More information about mosquito-borne illnesses can be found on the DPH’s website. “We also encourage everyone to make it a habit to check our online risk level maps for updates on when and where WNV activity is occurring,” said State Epidemiologist Dr. Catherine M. Brown.