CONCORD — State health officials say Eastern equine encephalitis has made its way into New Hampshire.

The N.H. Department of Health and Human Services reported Thursday that two emus in Fitzwilliam in southwestern New Hampshire and a horse in Derry have tested positive for the mosquito-bourne illness, which can be fatal in humans. The three are the first EEE cases to be confirmed in New Hampshire this year.

“Finding EEE in animals is indicative of an increased risk for humans,” said Beth Daly, chief of infectious disease surveillance for Public Health Services. “The type of mosquitoes that bite animals are the same type of mosquitoes that bite humans.”

The health department has raised the risk level in the affected communities in Cheshire and Hillsborough counties from “remote” to “high.”

Daly said it’s common in New Hampshire for mosquito-borne illnesses like EEE and West Nile virus to peak from late August through September. Both diseases can be transmitted to humans and have similar symptoms of high fever, severe headache, stiff neck and sore throat.

EEE, however, is much more serious. About one third of human cases of EEE result in death, Daly said.

Although the heat of summer has passed, mosquitoes will continue to be a danger until the first statewide hard frost — when temperatures cool to the point of hardening the ground.

“People often become complacent by the time the fall weather starts coming and aren’t as vigilant about using repellent,” Daly said. “It’s important, especially with finding these animals that have become infected with EEE, to continue the personal protective measures.”

Recommended precautions include wearing long pants and sleeves and using insect repellent containing DEET, especially during the evening and early-morning hours when mosquitoes are most active.

Health officials also recommend eliminating potential breeding areas commonly found in standing water, which can accumulate in old tires, ceramic pots or other containers and roof gutters that are not draining properly. The Health Department recommends changing water in birdbaths at least twice a week, aerating garden ponds or stock them with fish and removing old tires sitting around the property.

Some communities have also been spraying for mosquitoes, including the Rockhingham County town of Sandown. EEE was detected there late last month in a batch of mosquitoes, but no cases in animals or humans were found statewide before the two emus and horse started showing symptoms and tested positive, Daly said. All three cases were fatal.

The emus were in Fitzwilliam, just north of the Massachusetts stateline. The Massachusetts Department of Public Health announced Thursday that a woman in Amesbury has been hospitalized with EEE and is the sixth human case in the Bay State this year. One of the Massachusetts cases was fatal.

In New Hampshire, the state public laboratory has tested more than 4,000 batches of mosquitoes for EEE and West Nile virus. Of those, 40 batches tested positive for West Nile and three were positive for EEE.

Daly said EEE is mostly found in Eastern states and there is a national average of about six cases per year.

The last confirmed case of EEE in New Hampshire was found in a horse was in 2010. Since the state began testing in 2004, there have been 12 human cases of EEE, including two fatalities in 2005.

“It’s a very rare disease over all,” she said. “When they do occur, they can be severe and deadly.”

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Doug Alden may be reached at dalden@unionleader.com.