The Massachusetts Department of Public Health announced West Nile Virus has been detected in mosquito samples in Arlington, Boston and Waltham.
Positive mosquito samples were detected in Worcester, Brookline and Malden earlier this summer.
DPH reported that although there have been no human cases of West Nile Virus infection reported in the state this year, the current warm weather and pattern of precipitation events have produced large mosquito populations among the species most likely to spread the virus.
As a result of these findings, DPH has raised the risk level for human infection in the communities of Arlington, Belmont, Boston, Cambridge, Newton, Waltham and Watertown from low to moderate.
The Arlington Health Department urged residents Thursday to mosquito-proof their homes and avoid mosquito bites by using insect repellent when outdoors.
West Nile Virus is most commonly transmitted to humans by the bite of a mosquito infected with the virus. DPH reported there were 10 human cases of the virus in 2015.
While West Nile Virus can infect people of all ages, people over the age of 50 are at higher risk for severe infection.
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