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Massachusetts cities & towns where West Nile virus has been found

BOSTON — The Massachusetts Department of Public Health (DPH) has confirmed 25 human cases of West Nile virus (WNV) in the state this year.

The cases include:

  • A person in their 60s from Berkshire County who was exposed out-of-state
  • A man in his 60s from Bristol County who was hospitalized during his illness
  • A woman in her 20s from Essex County who was hospitalized during her illness
  • A man in his 60s from Essex County who was hospitalized during his illness
  • A man in his 70s from Essex County who was hospitalized during his illness
  • A man in his 70s from Hampshire County who was hospitalized during his illness
  • A woman in her 20s from Middlesex Country who was not hospitalized during her illness
  • A woman in her 40s from Middlesex Country who was hospitalized during her illness
  • A woman in her 50s from Middlesex Country who was not hospitalized during her illness
  • A woman in her 60s from Middlesex County who was not hospitalized during her illness
  • A woman in her 70s from Middlesex County who was hospitalized during her illness
  • A woman in her 70s from Middlesex County who was hospitalized during her illness
  • A woman in her 70s from Middlesex County who was hospitalized during her illness
  • A man in his 40s from Middlesex County who was hospitalized during his illness
  • A man in his 60s from Middlesex County who was not hospitalized during his illness
  • A woman in her 60s from Norfolk County who was hospitalized during her illness
  • A woman in her 50s from Suffolk County who was hospitalized during her illness
  • A woman in her 60s from Suffolk County who was hospitalized during her illness
  • A woman in her 80s from Suffolk County who was hospitalized during her illness
  • A man in his 50s from Suffolk County who was hospitalized during his illness
  • A man in his 50s from Suffolk County who was hospitalized during his illness
  • A man in his 60s from Suffolk County who was hospitalized during his illness
  • A man in his 80s from Suffolk County who was hospitalized during his illness
  • A person in their 30s from Suffolk County who was hospitalized during their illness
  • A woman in her 70s from Worcester County who was hospitalized during her illness

DPH raised the WNV risk level from moderate to high in Arlington, Boston, Belmont, Brookline, Cambridge, Chelsea, Everett, Lynn, Laden, Medford, Melrose, Newton, Revere, Saugus, Somerville, Watertown and Winthrop. Every other Massachusetts city and town has a moderate risk level.

A horse stabled in Granby was infected with WNV, became severely ill and had to be euthanized. An alpaca from Milford was also diagnosed with WNV.

So far this year, mosquitoes carrying WNV have been found in more than 150 cities and towns.

Risk from WNV will continue until the first hard frost. DPH cautions mosquitos still bite in autumn weather.

"We’ve seen four times as many WNV human cases this year in the Commonwealth than last year,” said Public Health Commissioner Monica Bharel, MD, MPH. "It's important that we continue to remember that even with the start of fall and its cooler temperatures, mosquito season isn't yet over.”

Last year, there were six human cases of WNV.

PH said the latest a person in Massachusetts became infected with WNV is November 5.

WNV is usually transmitted to humans through the bite of an infected mosquito. While WNV can infect people of all ages, people older than 50 are at higher risk for severe disease.

Most people infected with WNV will have no symptoms. When present, WNV symptoms tend to include fever and flu-like illness. In rare cases, more severe illness can occur.

Boston 25 News has created an interactive map, using blue markers to pinpoint the cities & towns where WNV has been found. The red markers indicate the counties where human cases of WNV have been confirmed. The green markers pinpoint the cities & towns where  Eastern equine encephalitis (EEE) has been found.

​​​​>>Related: What you need to know about mosquito-borne diseases