A horse from Rockingham County contracted the virus that causes Eastern equine encephalitis in the state’s first such case this year.

Wednesday’s announcement by the N.H. Department of Health and Human Services comes about two weeks after health officials reported three batches of mosquitoes with the deadly virus. The batches — comprising a species that feeds on birds, as well as one that bites both birds and mammals — were collected from Pelham, according to the state agency.

The horse is from Northwood, triggering the risk level for arboviral infection — viral illnesses spread by arthropods like mosquitoes and ticks — in that town to be raised to high. The surrounding communities of Barnstead, Barrington, Deerfield, Epsom, Nottingham, Pittsfield and Strafford are now considered at moderate risk, health officials said in a news release.

The horse was euthanized, as officials said EEE is generally more severe in horses and recovery is rare.

Meanwhile, on Tuesday, the state agency announced this year’s first finding of West Nile virus in mosquitoes in New Hampshire, in a batch collected last week from Manchester.

“We have had multiple positive tests for mosquito-transmitted viruses already this season in New Hampshire, and risk for human infection is likely to increase through the rest of the summer and fall,” Dr. Benjamin Chan, the state epidemiologist, said in Wednesday’s news release. “Eastern Equine Encephalitis in particular, can cause serious brain infection and neurologic disease.”

New Hampshire hasn’t had a human EEE case since 2014, when there were three.

On Sunday, the Massachusetts Department of Public Health announced that state’s fourth human EEE case this year, two days after announcing the third. The latest patient, Laurie Sylvia of Fairhaven, Mass., died over the weekend, according to news reports.

Earlier this month, New Hampshire’s health department announced that an adult resident of Kingston had tested positive for both the Jamestown Canyon and Powassan viruses, which are transmitted by infected mosquitoes and ticks, respectively. That person has recovered, officials said.

“With the holiday weekend approaching, we want people to enjoy outdoor activities, but it is critical for residents and visitors to take steps to prevent mosquito bites while outdoors,” Chan said in Wednesday’s news release.

That includes either avoiding being outside when mosquitoes are most active — from dusk to dawn — or wearing pants, long-sleeved shirts and socks, and using a mosquito repellent with up to 30 percent DEET, picaridin, para-menthane-diol or oil of lemon eucalyptus.

People can reduce mosquitoes’ presence in their homes by fixing screens and ensuring they’re tight-fitting and by using sweeping motions to get mosquitoes out from behind furniture and under beds and then killing them.

People can also make their properties less attractive to mosquitoes by eliminating weeds and tall grasses, as well as the standing water where they breed. This includes puddles in tires, rain gutters and recycling containers. The water in birdbaths should be changed twice a week at minimum, the state health department advises, and pools and hot tubs should be chlorinated and kept empty and covered if they’re not being used. Garden ponds can either be aerated or stocked with fish.

Tips for staying safe from ticks — which also spread Lyme disease, anaplasmosis and babesiosis — include wearing protective clothing, keeping grass short, frequently checking for ticks and removing them right away. Questions about arboviruses can be directed to the N.H. Bureau of Infectious Disease Control at 271-4496.