West Nile Virus

West Nile Virus is is an infection is transmitted by mosquitoes. West Nile Virus is a flavivirus commonly found in Africa, West Asia, and the Middle East. It is not known how long it has been in the United States, but CDC scientists believe the virus has probably been in the eastern US since the early summer of 1999, possibly longer. The virus can infect humans, birds, mosquitoes, horses, and some other mammals.


Symptons of severe West Nile Virus infection can include high fever, headache, neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness, vision loss, numbness and paralysis. These symptoms may last several weeks, and neurological effects may be permanent. Up to 20 percent of the people who become infected have milder symptoms such as fever, headache, and body aches, nausea, vomiting, and sometimes swollen lymph glands or a skin rash on the chest, stomach and back. Milder symptoms can last for as short as a few days, though even healthy people have become sick for several weeks. Approximately 80 percent of people (about 4 out of 5) who are infected with WNV will not show any symptoms at all. (more)

How It Spreads

Mosquitoes become infected when they feed on infected birds, which may circulate the virus in their blood for a few days. Infected mosquitoes can then transmit West Nile Virus to humans and animals when they bite.


The best way to prevent West Nile Virus infection is to avoid mosquitoes and prevent mosquitoes from breeding. (more)

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