Maine’s first case of West Nile virus in a human has been confirmed by federal health officials, but the person who had the disease did not contract it here, the state’s epidemiologist said Tuesday.

Dr. Stephen Sears said the federal Centers for Disease Control and Prevention diagnosed West Nile virus in a Pennsylvania woman who visited Maine but was not here during the incubation period for the virus, estimated at two days to two weeks.

As a result, the positive test was recorded as a Pennsylvania case. There have been no reports of humans contracting the virus in Maine.

State health officials got the positive test results Tuesday. The Pennsylvania woman was treated earlier this month at an emergency room in Lincoln County.

Test results from a patient in Maine who was suspected of having eastern equine encephalitis were negative, according to federal lab results.

“We thought (the West Nile case) would be positive,” said Sears. He said that, because the virus was contracted elsewhere, the test result “really doesn’t tell us anything” about the situation in Maine.

Infected mosquitoes transmit both West Nile virus and eastern equine encephalitis, so the diseases remain public health concerns through mid-October or after the first few hard frosts.

Some birds — including songbirds and crows — can carry the viruses, spreading them further into the mosquito population and, in turn, to other birds and to mammals, including humans.

A mosquito surveillance pool in York County tested positive for West Nile virus in mid-August. It was the first confirmed finding in the state.

West Nile virus has been found in humans in Massachusetts and New Hampshire, and Sears said health officials anticipate it will be detected in Maine.

He said the message from the case confirmed Tuesday “should actually be consistent with information already provided” by the state: Be aware, but not afraid, of the disease — and certainly not panic-stricken by its appearance in Maine.

State officials have encouraged residents and visitors to heed longstanding suggestions for minimizing exposure to mosquitoes, Sears said. That includes staying indoors between dusk and dawn, wearing loose long-sleeved shirts and full-length pants, and using mosquito repellent if you must be outdoors after dark, when mosquitoes are most active.

Widespread pesticide spraying has been done in New Hampshire and Massachusetts. In Maine, one school district has used pesticide — a minimal-risk botanical blend — around two elementary schools.

Edges of the school properties in Lebanon were sprayed a week ago, the district verified through the pesticide application firm Atlantic Pest Solutions of Arundel.

School officials decided not to use synthetic pesticides because they felt the botanical blend — essentria IC3 — offered enough protection and reduced toxicity to students and other residents who might use the grounds for athletic events or recreation.

Essentria IC3 is a combination of rosemary and peppermint oils and geraniol (a derivative of geraniums) as active ingredients and wintergreen and white mineral oils, vanillin and polyglyceryl oleate (an emulsifier).

The botanical pesticide, which is not as powerful as synthetic chemical blends, has a residual toxicity of two to four weeks. It is “non-selective,” meaning it does not target a specific species and will kill insects besides mosquitoes, including bees, ants, crickets, cockroaches, fleas, ticks and spiders.

School officials “felt that it was a middle-of-the-road (choice), and they wanted to do something,” said Ted St. Amand, owner of Atlantic Pest Solutions.

Because it has an oily base, it should stick to the undersides of leaves and crooks of tree branches, where adult mosquitoes are likely to be during the day, when spraying is done.

Staff Writer North Carin can be contacted at 791-6325 or at:

ncairn@mainetoday.com