Health departments throughout the country are urging residents to take precautions, including removing sources of standing water, avoiding mosquito-prone areas and applying a mosquito repellent.
According to reports, several batches of mosquitoes are testing positive for the West Nile virus.
West Nile virus, a disease transmitted through the bite of a mosquito that has picked up the virus by feeding on an infected bird, has plagued certain states and sent some residents running for EPA-registered insect repellent.
Health officials from the U.S. Centers for Disease Control and Prevention say about one in 150 people infected with West Nile virus will develop severe illness.
The severe symptoms can include high fever, headache, neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness, vision loss, numbness and paralysis, the agency adds.
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These symptoms may last several weeks, and neurological effects may be permanent, and most people with the virus have no clinical symptoms of illness, but some may become ill three to 15 days after being bitten.
Health officials say a total of 61 human cases were reported in Illinois last year, the first on Aug. 31.
Only about two people in 10 who are bitten by an infected mosquito will experience any illness — which is usually mild and includes fever, headache and body aches, but serious illness, such as encephalitis and meningitis, and death are possible, according to the Illinois Department of Public Health.
Joe Conlon, a technical adviser to the American Mosquito Control Association, said he encourages people to check for depressions on their property that may hold water.
I've seen mosquitoes breeding in everything from air conditioner drip pans to ditches to wood piles, Conlon told ABC News. This year is going to be a wake up call for people.
In Wisconsin, the first animals to test positive for the West Nile virus in Wisconsin this year were birds, according to state and county health officials who announced Wednesday that two birds tested positive for the virus.
Other health officials on Long Island have decided to close a county park during nighttime hours after a mosquito there tested positive for the West Nile virus.
Suffolk County's health commissioner told Long Island paper, Newsday, that Blydenburgh County Park in Smithtown will close at 6 p.m. daily, when mosquitoes start to become more active. It will reopen at 8 a.m.
The West Nile virus is mild for most people, but can be deadly for others with weak immune systems.
Suffolk Health Commissioner James Tomarken says the presence of the virus in the park's mosquito population is no cause for alarm, but said residents should still consider covering up when they are outside in the evenings.
The New York Times reported Tuesday that mosquitoes in the area, New York City officials announced last week, had shown traces of West Nile virus.
A press release from the New York City Department of Health and Mental Hygiene, said:
Since June 30th, West Nile virus has been identified in 80 mosquito pools collected in all NYC boroughs except Manhattan, with most activity in Brooklyn, Queens and Staten Island. Mosquito pools from New Jersey, Connecticut, Pennsylvania, Massachusetts, and New York State have also tested positive for West Nile virus this season.
People older than 50 have the highest risk of severe disease.
The department suggested that health providers advise their patients, especially adults 50 years and older, to protect themselves from mosquito bites.
However, the species of mosquitoes that tend to breed in rain water are not those most responsible for the spread of West Nile virus, said Dr. Waheed K. Bajwa, executive director of the health department’s Office of Vector Surveillance and Control, the Times reports.
“There are more and more breeding grounds, so the population will go up,” Dr. Bajwa said of mosquitoes in general. “But this is not going to impact mosquitoes which are responsible for the transmission of the disease.”