Mass. health officials announce 12th human case of West Nile Virus

Massachusetts health officials have confirmed the state’s 12th human case of West Nile virus this year, prompting them to raise the risk level in two communities.

The Massachusetts Department of Public Health (DPH) announced Friday that a woman in her 60s contracted the mosquito-borne illness and was likely exposed in Norfolk County. In response, officials raised the West Nile virus risk level to high in Milton and Quincy.

The risk also remains high in Boston, Brookline, Cambridge, Chelsea, Everett, Malden, Newton, Revere, Somerville, Watertown, and Winthrop, according to DPH. Most other parts of the state are currently considered at moderate risk.

Officials warned that the threat of West Nile virus will remain until the state gets its first hard frost, which typically happens between mid-October and early November.

Massachusetts detected its first West Nile-positive mosquitoes of the season on June 16. Since then, 340 mosquito samples have tested positive across 13 counties, including Barnstable, Berkshire, Bristol, Dukes, Essex, Franklin, Hampden, Hampshire, Middlesex, Norfolk, Plymouth, Suffolk, and Worcester counties.

No animal cases of West Nile virus have been reported this year, DPH said.

Health officials are also monitoring eastern equine encephalitis (EEE). Twenty-seven mosquito samples have tested positive for the virus so far this year, though Massachusetts has not reported any human or animal cases, according to the health department.

DPH is urging residents to continue taking precautions against mosquito bites, particularly from dusk to dawn, when many mosquitoes are most active. Officials recommend using an EPA-registered insect repellent and wearing long sleeves, long pants, and socks when outdoors.

Residents can also reduce mosquito populations around their homes by emptying containers that collect standing water, cleaning gutters and drains, regularly changing water in birdbaths, and making sure window and door screens fit tightly, DPH said.

Horse and other animal owners should also dump standing water and consult their veterinarians about mosquito repellents and vaccinations against West Nile virus and EEE, officials said.

DPH updates mosquito-borne illness cases and community risk levels daily through its Massachusetts Arbovirus Update dashboard. 

“DPH encourages everyone to use this online resource regularly to stay informed on risk levels in their community and around the state,” the department said in a press release. “People have an important role to play in protecting themselves and their loved ones from illnesses caused by mosquitoes.”