Health officials confirmed the first human case of West Nile virus in Boston this year in the wake of Massachusetts moving into a “moderate” risk level for the mosquito-borne infection.
The Massachusetts Department of Public Health raised the risk level from low to moderate on Tuesday, marking the second time ever the agency has raised that risk level statewide. The Boston Public Health Commission confirmed the city’s first case of infection on Friday. A fourth case of West Nile virus in Massachusetts was confirmed in Middlesex County on Monday.
An investigation by state health officials indicated that at least two of the four human West Nile virus cases were exposed in Greater Boston. Officials announced on Monday that they were raising the risk level from moderate to high for 11 communities: Arlington, Boston, Belmont, Brookline, Cambridge, Chelsea, Everett, Medford, Newton, Somerville and Watertown.
What is West Nile virus?
West Nile virus is a viral infection spread by mosquito bites. Though most people — 8 out of 10, according to the Centers for Disease Control and Prevention — infected do not have any symptoms, the virus can cause high fever and flu-like illness. In rare cases, people can develop severe, sometimes fatal, illness.
There are currently no vaccines to prevent, nor medication to treat West Nile virus in humans. West Nile virus can infect anyone, according to the Massachusetts Department of Public Health, but those over the age of 50 are at a higher risk for more severe disease.
The Boston West Nile virus patient was a woman in her 50s who was hospitalized and has since been discharged. Last year, there were no human cases of West Nile virus in Boston, officials said.
West Nile virus in Massachusetts
Bacteriologist Erik Devereaux holds a mosquito that he will check for the West Nile Virus July 28, 2000 at the State Lab in Boston. Photo: Getty Images
It is not yet known if this patient was infected with West Nile virus while in Boston, officials said, but mosquito pools throughout the city have tested positive for virus. Local officials will continue to investigate.
There have now been four confirmed case of West Nile virus in Massachusetts this year, with officials reporting the most recent case on Monday. Officials across the state are urging residents to take precautions against mosquito bites.
“The hot, humid weather in Massachusetts combined with frequent heavy rainfall has provided perfect conditions for mosquito species carrying West Nile Virus to breed,” said Public Health Commissioner Monica Bharel in a statement. “I strongly encourage everyone to keep using insect repellent and to be especially aware of mosquito activity at dusk and dawn when the risk of being bitten by mosquitoes is greatest. Move indoors if you are getting bitten.”
Most human West Nile virus cases occur in August and September, according to DPH State Epidemiologist Dr. Catherine Brown, which is part of why state officials have ramped up the risk level.
Officials are encouraging Massachusetts residents to use insect repellent with an EPA-registered ingredient when outdoors, to be aware of peak mosquito hours (from dusk to dawn), to wear long-sleeves, long pants and socks when outdoors and to mosquito-proof your home by draining standing water and installing or repairing screens. You should protect your pets, too, as animals can get the virus, you can speak with your veterinarian about mosquito repellents approved for use in animals.
