The state Department of Public Health on Friday announced the third human case of mosquito-borne West Nile virus this year. The patient is a resident of Middlesex County in her 60s. She was hospitalized during her illness but has returned home.
State epidemiologist Dr. Catherine Brown blamed this fall's unusually warm weather for prolonging the mosquito season. The risk will continue until the first hard freeze.
The other two cases were a Bristol County man in his 50s and a Hampden County man  in his 60s. 
In 2016, there were 16 human cases of West Nile in Massachusetts.

The risk level for West Nile remains as moderate in many communities in Bristol, Norfolk and Plymouth counties, including Abington, Acushnet, Attleboro, Bridgewater, Brockton, Dartmouth, Dedham, Dighton, East Bridgewater, Fairhaven, Halifax, Hanson, Holbrook, Kingston, Milton, Needham, New Bedford, Norton, Norwell, Pembroke, Plymouth, Plympton, Quincy, Rehoboth, Rockland, Seekonk, Swansea, Taunton, Wellesley, West Bridgewater and Whitman. 

The virus has been detected in tests from June 26 through Sept. 27: Abington (3), Bridgewater, Brookline, Brookline, Dartmouth, Dedham (3), Dighton, Fairhaven, Franklin, Freetown, Halifax, Holbrook, Kingston, Lakeville, Marion (2), Middleboro (2), Millis, Needham, Norton (2), Plymouth (2), Quincy, Rehoboth (5), Seekonk (3), Swansea (2), West Bridgewater (2) and Whitman (2).

Statewide, 289 mosquitoes tested positive for West Nile, up from 189 in 2016.

The only positive test for the more dangerous encephalitis virus was on mosquitoes collected in Westport. The risk level for encephalitis is considered low statewide.

In 2016, there were 16 human cases of the mosquito-born infection identified in Massachusetts.

While the virus can infect people of all ages, people over the age of 50 are at higher risk for severe disease. Most of those who become infected are unaware of it, but fever and flu-like symptoms are possible. In rare cases the illness can be severe. 

The state Department of Public Health reported 14 human cases of West Nile virus in 2016. Ten of the cases were in Middlesex County, two in Norfolk County and one each in Essex and Suffolk counties.

In 2015, 10 human cases of West Nile were reported in the state.

For more information about mosquito-borne illnesses, visit the Department of Public Health's website or the U.S. Centers for Disease Control.