State Public-health Officials Warn of West Nile Virus Risk

BOSTON — The Massachusetts Department of Public Health (DPH) announced that 36 additional communities are now at moderate risk for West Nile virus (WNV), bringing the total number of communities at moderate risk to 59 spread across eight counties. Moderate risk means mosquito activity is substantial enough that people should use personal protection to avoid being bitten by a mosquito. There have been no human cases of WNV this year.

The eight counties are Hampden, Hampshire, Franklin, Essex, Middlesex, Norfolk, Suffolk, and Worcester counties. The Pioneer Valley and Worcester and its surrounding communities are experiencing more West Nile virus positive mosquito activity this year than in a typical season, said DPH Deputy State Epidemiologist Dr. Catherine Brown.

“The Boston area is usually a focus of WNV activity, but this year we are seeing evidence of widespread WNV infection in mosquitoes with particularly significant activity in and around Worcester and in the Pioneer Valley,” she noted. “I encourage everyone to use the tools of prevention, including applying mosquito repellent with an EPA-registered ingredient according to the directions on the label; wearing clothing to reduce exposed skin when weather permits; draining standing water to prevent mosquito breeding; and repairing window screens to keep mosquitoes out of your home. August and early September are when we see most of our WNV infections in people.”

WNV is usually transmitted to humans through the bite of an infected mosquito. In 2016, there were 16 human cases of WNV infection identified in Massachusetts. While WNV can infect persons of all ages, people over the age of 50 are at higher risk for severe disease. Most people infected with WNV will have no symptoms. When present, West Nile symptoms tend to include fever and flu-like illness. In rare cases, more severe illness can occur.