Residents across Massachusetts are being urged to stay inside at night after a deadly mosquito-transmitted illness appeared in the state.

Earlier this month, Massachusetts health officials confirmed that a man in his 80s living in Worcester County, west of Boston, had contracted the first human case of eastern equine encephalitis virus in the state this year.

We have not seen an outbreak of EEE for four years in Massachusetts, Robbie Goldstein, the states department of public health commissioner, said in a statement published by the Washington Post . We need to use all our available tools to reduce risk and protect our communities. We are asking everyone to do their part.

Heightening fears the virus may be spreading across New England, on Tuesday, health officials in New Hampshire reported a man in the state who tested positive for mosquito-borne illness had died. The last case reported in New Hampshire was in 2014.

The infection, also known as sleeping sickness, stems from the bites of infected mosquitoes and can carry serious risks, according to the Centers for Disease Control and Prevention.

While rare, the virus is fatal in about 30% of cases.