The man whom health authorities announced this week is Massachusetts' first human case of West Nile virus this year is from Cambridge, the city's public health department announced Friday.
He is in his 60s and was hospitalized after he became ill in early September, according to the Cambridge Public Health Department.
The department believes he was infected by mosquitoes in Cambridge that carried the virus.
The state announced the case on Wednesday, and Cambridge health officials said that the risk level of West Nile infection was raised from low to moderate Thursday for the city and much of greater Boston: Arlington, Belmont, Brookline, Boston, Newton, Somerville and Watertown.
There were 49 cases of West Nile virus in Massachusetts last year, but this year, the risk of human infection is considered generally low, officials said.
"We have not seen much West Nile virus activity this year,” Public Health Commissioner Monica Bharel said in a statement Wednesday. "Still, today's news is a compelling reminder that we all need to continue to take steps to protect ourselves and our families from mosquito bites."
Cambridge's chief public health officer echoed that sentiment Friday, writing in a statement, "We urge residents to take precautions against mosquito bites, especially after dusk."
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Symptoms of encephalitis or meningitis associated with West Nile virus include fever, flu-like illness, headache, neck stiffness, stupor, tremors, muscle weakness and paralysis. People at greatest risk of severe illness are over 50 or have weakened immune systems.
Another mosquito-borne virus, eastern equine encephalitis, has infected seven people in the state this year, one of whom has died, according to health officials. See a map the parts of Massachusetts at risk of infection.