¹A 'Pool' is a laboratory term, meaning a collection of 10-60 individual mosquitoes of the same species from a particular site. Individual mosquitoes are not submitted for testing.
Background and Basics:
West Nile Virus (WNV) is a mosquito-borne infection that can cause serious illness, and sometimes death. It is named after the West Nile region of Uganda, where the virus was first discovered. An outbreak in New York State in 1999 was the first time the virus had ever been seen in the Western Hemisphere.
Signs and Symptoms:
Most people who are infected with WNV will not show any symptoms. It is estimated that 20 percent of the people who become infected will develop West Nile fever and have mild symptoms, including fever, headache and body aches, and occasionally a skin rash and swollen lymph glands. The symptoms of severe infection (West Nile encephalitis or meningitis) can include headache, high fever, neck stiffness, muscle weakness, stupor, disorientation, tremors, convulsions, paralysis and coma. It is estimated that one in 150 persons infected with the WNV will develop the more severe form of the disease. Usually, symptoms occur from 3 to 14 days after being bitten by an infected mosquito. There is no specific treatment for viral infections, other than to treat the symptoms and provide supportive care.
All residents of areas where virus activity has been identified are at risk of getting WNV; New York State has a moderate amount of West Nile virus every year. Persons over 50 years of age are at the highest risk for severe disease. People can reduce their chances of getting WNV by reducing their chances of getting bit by mosquitoes. Get rid of mosquito breeding sites, minimize outdoor activities when mosquitoes are most active and use personal protection- long sleeves and pants or use of a repellent. (Click here to learn how to keep your home mosquito-free)
WNV is primarily transmitted through the bite of an infected mosquito. Mosquitoes become infected when they feed on infected birds. WNV has been transmitted by blood transfusion ororgan transplantation in a small number of cases. As a result, U.S. blood collection agencies are screening blood donations for the presence of the virus. These transfusion- and transplant-related cases make up a small percentage of those infected with WNV. Although persons needing blood transfusions or organ transplants should be aware of the risk of WNV infection, the benefits of receiving needed transfusions or transplants outweigh the potential risk for infection. Transplacental transmission (pregnant woman to unborn child) and transmission through breast-feeding have also been documented. The number of these cases is small. Pregnant women should consult their health care provider for more information.
Pets occasionally get WNV from mosquito bites, but very seldom get sick. Horses are more susceptible to serious illness from WNV than are dogs and cats. Natural infection of a pet by contacting or eating an infected dead bird has not been documented. Most mosquitoes do not transmit disease. While there are about 70 different species of mosquitoes in New York State, only certain species have been associated with WNV.