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West Nile Virus (WNV): Facts and Details

What is West Nile Virus?

West Nile Virus (WNV) is a virus that can infect humans, birds, mosquitoes, horses and other mammals.

How is WNV spread?

Most often, WNV is spread by the bite of an infected mosquito. Mosquitoes become infected when they feed on infected birds. Infected mosquitoes can then spread WNV to humans and other animals when they bite.

In a very small number of cases, WNV also has been spread through blood transfusions, organ transplants, breastfeeding and even pregnancy from mother to baby.

WNV is not spread through casual contact such as touching or kissing a person with the virus.

What are the symptoms of WNV?

Approximately 80 percent of individuals who are infected with WNV will not show any symptoms at all. Those who become infected with WNV may develop 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.

Severe symptoms of WNV can include high fever, headache, neck stiffness, stupor, disorientation, tremors, convulsions, muscle weakness, vision loss, numbness, paralysis, and coma.

How soon do symptoms appear after infection occurs?

People typically develop symptoms between 3-14 days after being bitten by an infected mosquito. Individuals with mild illness may exhibit symptoms for only a few days, although even healthy people have become sick for several weeks. Individuals with severe illness may exhibit symptoms for at least several weeks, and neurological effects may be permanent.

How is WNV treated?

There is not specific treatment for WNV infection. In more severe cases, people usually need to go to the hospital where they can receive supportive treatment including intravenous fluids, help with breathing, and nursing care.

What should I do if I think I have WNV?

Milder WNV illness improves on its own and people do not necessarily need to seek medical attention, though they may choose to do so. If you develop severe symptoms of WNV, such as confusion or unusually severe headaches, seek medical attention immediately. Severe WNV illness usually requires hospitalization. Pregnant women and nursing mothers are encouraged to talk to their doctor if they develop symptoms that they feel could be WNV.

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