Maine has recorded the year’s first case of the potentially deadly West Nile virus in mosquitoes in York County.

The Maine Center for Disease Control and Prevention is investigating whether West Nile and another disease carried by mosquitoes called Eastern equine encephalitis may have infected two people, according to Dr. Stephen Sears, state epidemiologist.

A mosquito collection site that the state regularly checks for both diseases tested positive for West Nile virus, Sears said. The results were confirmed Friday, he said.

“People need to be aware, but not alarmed,” Sears said.

Maine has never had a human case of West Nile, but the virus is making a comeback nationally. Nearly 700 people in the United States have been infected with West Nile this year, the most since the virus first was detected in the U.S. in 1999. This year has seen 26 deaths from the disease.

Mosquitoes pick up the disease from biting infected birds and then spread the virus to people.

The possible human cases in Maine have not been confirmed. One involves someone who may have been infected out of state, Sears said. Test results will take at least a week, he said.

“Those people are all doing fine,” Sears said. “We are working to see whether in fact it could have been a case of these diseases.”

The year’s first confirmed case of West Nile in mosquitoes came as no surprise to health officials. The positive test results in York County came two weeks after the Maine CDC warned health providers to be on the lookout for West Nile as the virus cropped up in mosquitoes elsewhere in New England, including New Hampshire.

“We probably will find others,” Sears said. “This is part of ongoing surveillance.”

The state last recorded West Nile in mosquitoes two years ago at a testing site.

Maine joins the ranks of more than 40 other states that have reported West Nile virus infections this year in people, birds or mosquitoes.

Almost half of this year’s cases have been reported in Texas. Mississippi, Louisiana, Oklahoma, South Dakota and California account for another third of the cases in 2012.

Most people infected with West Nile don’t show any symptoms. About one in five gets sick with a fever, body aches, vomiting and joint pain that can last from a few days to several weeks. Symptoms typically appear between three and 14 days after a bite from an infected mosquito.

In severe cases, which are more common in people 50 and older, the virus causes neurological problems such as brain swelling that can lead to confusion, coma, seizures and permanent damage.

For some, the disease is fatal.

There is no treatment or human vaccine for West Nile. The disease is not spread by close contact with someone infected with the virus.

Health officials aren’t sure what’s causing the rise in West Nile this year, but suspect the weather may play a role.

“It’s a very complicated ecologic system between mosquitoes, birds, weather, rain,” Sears said. “We don’t really understand all of it. We just know that this year, in monitoring everywhere in the U.S. it appears to be a very significant year for West Nile.”

Health officials are also on the alert for Eastern equine encephalitis. No mosquitoes have tested positive for the disease this year, but research studies of deer indicate that the illness has reappeared in Maine after killing a number of horses in the state in 2009, according to Sears.

The symptoms are similar to West Nile, but Eastern equine encephalitis can be more deadly, leading to death in 35 to 50 percent of cases.

To lower your risk of getting infected with either disease, the CDC recommends:

• Use insect repellent containing an EPA-registered active ingredient when outdoors.

• Try to stay indoors at dusk and dawn, when mosquitoes are most active. Wear long sleeves and pants if you plan to be outside.

• Install door and window screens and repair any holes to keep mosquitoes out.

• Empty standing water where mosquitoes can breed, such as from flower pots, buckets and barrels. Change the water in pet dishes and replace the water in bird baths every week. Drill holes in tire swings to allow water to drain. Empty kiddie pools when they’re not in use and store them on their side.

• Don’t handle a dead bird with your bare hands. Contact your local health department for instructions on reporting and disposing of it.

Jackie Farwell

I'm the health editor for the Bangor Daily News, a Bangor native, a UMaine grad, and a weekend crossword warrior. I never get sick of writing about Maine people, geeking out over health care data, and...