Massachusetts residents are now at a heightened risk for West Nile virus, as a fourth case of the mosquito-borne disease was discovered last week.
The most recent person infected is a woman in her 50s from Middlesex County, according to a report from the Boston Globe. She was never hospitalized for the illness. The other three cases, which were reported on Friday, involve a Worcester County woman in her 70s, a woman in her 60s from Middlesex County, and a woman in her 50s from Suffolk County.
At least two of the four patients were exposed to the virus in the Greater Boston area, the report said. As a result, state workers have raised the risk level from moderate to high for 11 communities that include Arlington, Boston, Belmont, Brookline, Cambridge, Chelsea, Everett, Medford, Newton, Somerville, and Watertown.
Massachusetts residents are urged to take precautions.
“This means staying indoors, or using bug spray or clothing that covers the body – pants and long sleeves, especially between dusk and dawn when the mosquitoes that transmit West Nile are most active,” said Dr. Joseph Gross, an infectious disease specialist at Beverly Hospital.
“Like many other viruses, people who are older and those who are immunocompromised are at higher risk of severe illness,” said Mark Gendreau, MD, Chief Medical Officer at Beverly and Addison Gilbert Hospitals.
August and September are the height of mosquito population.
About 1 in 5 people develop a fever due to West Nile virus, according to the Centers for Disease Control and Prevention. About 1 in 150 develops more serious symptoms that could require hospitalization.
The disease has been reported in every state in the U.S. Last year, there were six human cases of West Nile virus in Massachusetts.
Officials raised the statewide risk level for West Nile virus on Aug. 21. The statewide risk was raised only one other time, in 2012, when 33 human cases of West Nile were recorded in Massachusetts.
Most patients with non-neuroinvasive West Nile disease or West Nile meningitis recover completely, but fatigue, malaise and weakness can linger for weeks or months
There is no specific treatment for West Nile disease. Patients with severe meningeal symptoms often require pain control for headaches and treatment for associated nausea and vomiting.
“It is not a cause for panic, but it is a disease that can cause severe illness, and everyone should be vigilant in protecting themselves,” said Dr. Gross.