FAQ ­ Mosquitoes and West Nile Virus

Q. What is West Nile Virus?
A. West Nile Virus is a mosquito­-borne disease that can cause encephalitis or a brain
infection. Mosquitoes acquire the virus from birds and pass it on to other birds, animals and people. In 1999, West Nile Virus first appeared in New York. Mosquitoes spread this virus after they feed on infected birds and then bite people, other birds and animals. It is not spread by person-­to­-person contact and there is no evidence that people can get the virus by handling infected animals. West Nile encephalitis is caused by West Nile virus, a flavivirus previously only found in Africa, Eastern Europe, and West Asia. West Nile virus is closely related to St. Louis Encephalitis virus (SLE), which is found in the United States.

Q. How does West Nile Virus spread?
A. Mosquitoes can become infected with West Nile Virus by feeding on birds that have the virus in their bloodstream. Once a mosquito is infected with the virus it can transmit the virus to humans, birds, horses or other mammals through a bite. People can only become infected with West Nile Virus after being bitten by an infected mosquito. There is no evidence that people can get West Nile Virus from infected animals or people, or that people can transmit the West Nile Virus to other animals, birds or people.

Q. Who is most at risk?
A. People over 50 years of age have the highest risk of developing a severe illness because as we age, our bodies have a harder time fighting off disease. People with compromised or undeveloped immune systems are also at increased risk; however, anyone can get the virus.

Q. What are the symptoms of West Nile Virus infection?
A. Most people bitten by infected mosquitoes do not develop any symptoms. However when symptoms of infection do occur, they usually appear 5­-15 days from the time you were bitten. Most people who are infected show no or only mild symptoms such as low grade fever, headache, and occasionally swollen lymph glands. More severe signs and symptoms can include high fever, stiff neck, muscle weakness, disorientation, brain inflammation (encephalitis), coma and rarely, death. There is no specific treatment for West Nile Virus; however, in more severe cases, intensive supportive therapy is indicated.

Q. What should I do if I think I have been infected with West Nile Virus?
A. Contact your family physician.

Q. If I live in an area with positive birds and mosquitoes will I get West Nile Virus?
A. It is highly unlikely. Even in areas where mosquitoes do carry the virus very few
mosquitoes are infected (less than 1%). If the mosquito is infected, less than 1% of people
who get bitten and become infected will get severely ill. The chances that you will become
severely ill from one mosquito bite are extremely small.