Mosquitoes in Cumberland County have tested positive for West Nile virus, less than a week after the state recorded its first case of the virus this year in mosquitoes in York County.
In a public health update issued Thursday, the Maine Center for Disease Control and Prevention said West Nile was found in a mosquito trap in Gorham. The virus was detected following last Friday’s confirmation that mosquitoes in York County carried the disease.
The York County mosquitoes that tested positive for the virus were collected in the town of Lebanon. This is the earliest that West Nile has been identified in mosquitoes in Maine, the update said.
Most infections from the potentially deadly disease are reported in August and September. Maine last recorded West Nile in 2010 at a single mosquito trap.
The state routinely collects mosquitoes at a number of traps and checks them for disease.
Dr. Stephen Sears, state epidemiologist, said in a news release that an increase in mosquito-borne disease activity is expected to continue in Maine and that more positive tests in mosquito pools is likely.
Manchester, N.H. is spraying to kill mosquitoes after health officials announced a city adult has the first confirmed human case of West Nile Virus in the state in two years.
The Maine CDC is investigating whether West Nile and another disease carried by mosquitoes called Eastern equine encephalitis may have infected two people.
Maine has never had a human case of West Nile, but the virus is making a comeback nationally. More than 1,100 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 41 deaths from the disease.
Mosquitoes pick up the disease by 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.
Maine’s first cases of West Nile in mosquitoes this year come as federal officials declared the current outbreak one of the largest in the U.S., with four times the usual number of cases for this time of year.
The Maine cases 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.
Multiple mosquito traps in New Hampshire have tested positive for West Nile and the disease has been found in people and horses in Massachusetts.
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 illnesses have been reported in Texas.
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.
Health officials are also on the alert for Eastern equine encephalitis. No mosquitoes have tested positive for the disease in Maine this year, but research studies of deer indicate that the illness has reappeared in the state after killing a number of horses in 2009.
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.
The Maine CDC will post weekly reports through September on mosquito-borne disease surveillance at maine.gov/dhhs/mecdc/infectious-disease/epi/vector-borne/arboviral-surveillance.shtml.
Information on pesticides and repellents is available at the Maine Board of Pesticides Control website at maine.gov/agriculture/pesticides/public/#mosquito
The Associated Press contributed to this report.