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. For the first time, in the summer of 2000, Pennsylvania found the virus in mosquitoes, birds and a horse. Mosquitoes spread this virus after they feed on infected birds and then bite people, other birds and animals. West Nile virus cases occur primarily in the late summer or early Fall, although the mosquito season is April through October.
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. 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 immune systems are also at increased risk, however, anyone can get the virus. People with mild infections may experience fever, headache, body aches, skin rash and swollen lymph glands. People with more severe infections may experience high fever, headache, neck stiffness, stupor, disorientation, coma, tremors, occasional convulsions and paralysis.