Prompted by recent positive test results for mosquito-borne diseases in other New England states, some Maine communities are gearing up for what some local officials fear might be a particularly nasty year for Eastern Equine Encephalitis and West Nile virus.

“We could be in for a bad year,” said Rob Yandow, town manager in York, where testing of mosquito pools was started June 1, about four to six weeks earlier than in many Maine towns and cities.

In Maine, both viruses were first detected in 2001 in birds, and in 2012 – a particularly bad year for the viruses – the state reported the first human case of West Nile believed to be contracted here.

In New Hampshire, health officials this week identified two human cases of the mosquito-transmitted virus chikungunya in a couple who had been traveling in the Caribbean. Relatively rare and only recently detected in the U.S., this virus is seldom fatal but it can be debilitating, with symptoms that include headache, muscle pain, joint swelling and rash, according to the state’s Department of Health and Human Services.

The earliest detection of EEE ever recorded in Vermont occurred June 17 at a mosquito test site in a county bordering Canada – surprising for being so early and so far north, health officials said.

High season for mosquito-borne diseases tends to run from July 15 through August, Maine health officials said. Some cases are still found in the fall before the first frost knocks down mosquito populations.

“We had a really bad year last year,” Yandow said. Tests of pools containing mosquito larvae in York last summer turned up more than two dozen positive results, the majority for EEE and about 25 percent for West Nile, he said.

“We had one mosquito pool that had both,” Yandow said.

Statewide, more than 25 testing sites are strategically located from southern Maine to Bangor, said Dr. Sheila Pinette, director of the Maine Center for Disease Control and Prevention. “We suspect that (EEE) is here already,” she said.

Over the course of the summer, she said, the state can test 1,000 pools. Test sites are chosen based on where livestock or wildlife, such as horses, deer and moose, have tested positive for viruses in the past.

In 2009, Maine experienced an unprecedented rate of EEE incidence with 19 animals and two mosquito pools testing positive for the virus. In fall 2008, a man vacationing in Cumberland County died of the disease, though it was never confirmed that he was infected while in Maine.

In 2013, Maine reported EEE in horses in Oxford and Somerset counties, as well as a horse, an emu, a pheasant and 26 mosquito pools in York County. Thirty pheasants in Lebanon died after being infected in 2012.

EEE is the more dangerous of the two viruses. It occurs in the eastern half of the nation, and causes disease in humans, horses and some bird species, according to the state CDC. Many people infected with EEE will experience no obvious symptoms. Those who do become ill may have symptoms ranging from mild-flu like illness to inflammation of the brain, coma and death. Among those developing severe cases of EEE, up to 33 percent die and most survivors suffer some brain damage, according to the federal Centers for Disease Control and Prevention.

West Nile occurs throughout the U.S., and has been prevalent in Southern states, particularly Texas, in recent years. It can cause disease in humans as well as birds and other mammals. Many persons infected with West Nile virus will have no obvious symptoms. In those persons who do become ill, symptoms include headache, high fever, altered mental state, tremors, convulsions and rarely, paralysis. West Nile virus can also cause meningitis/encephalitis and be fatal.

“But no panic, no panic, no panic,” said Pinette. She emphasized that although the positive test result in Vermont was unusually early for that state, it reflected a consistent trend throughout New England over the past several years, with early detections found under very different conditions and habitats. In Maine, the first positive test in a mosquito pool generally is found at the end of July, she said.

Based on statewide and local history of the diseases in Maine and New England, Yandow issued what he now considers a routine precaution at the regular York Board of Selectmen’s meeting this week. The town began testing mosquito pools for EEE and West Nile virus about a month to six weeks early.

“We haven’t had a human case (ever),” Yandow said. “But it’s just a matter of time, I think.”

Other communities that have begun testing earlier than usual include Kittery, which with York is one of only two communities licensed by the state to use larvacide, a pesticide designed to kill mosquitoes before they reach their adult stage and begin to bite.

Mosquito-borne diseases are transmitted by infected insects through biting, which spreads the illnesses into human blood.

Lebanon, also in York County, is not testing or spraying at this point, said Cherry Lord, executive assistant to the city manager. “Typically, we don’t see it until mid- to late August,” she said.

Last year, Lebanon became the center of some public debate and controversy when officials authorized spraying near elementary schools as a preventive measure to protect children as young as 6 and through middle school. The spraying was deemed necessary, because the town’s two elementary schools are separated by a 100-foot-wide thicket of woods with a brook.

School officials in Lebanon were not available to comment Thursday on whether spraying might be considered this year, but the town does no testing. Only state test sites are set up there.

In nearby Sanford, testing has not yet begun, said City Manager Steven Buck. That community in the past has opted for a regional forum to promote public awareness, and in 2012 the school department sprayed around buildings and playing fields, he said.

Town and health officials emphasized the need for preventive measures in and around homes. People should avoid being outside at dawn or dusk, when the insects are especially active, and health officials recommend the proper use of insect repellents – synthetic or organic.

They advised residents to dispose of tin cans, plastic containers, ceramic pots or other water-holding containers. Leaf debris should be removed and brush trimmed to reduce mosquito-attracting habitat.

As the weather gets warmer, parents are advised to turn over plastic wading pools and wheelbarrows when they are not in use. It is recommended that birdbaths be kept clean – and empty when not in use.

Birds are also affected by the mosquito diseases. Health officials this year, as in the past, have asked that people report findings of three or more dead birds together in one location to the Maine CDC.