Symptoms & Treatment

West Nile virus is a potentially serious but preventable viral illness most often spread by the bite of an infected mosquito. Mosquitoes become infected when they feed on infected birds. The virus is not spread from person-to-person.

No symptoms in most people: Approximately 80 percent of people (about 4 out of 5) infected with West Nile virus will not show any symptoms at all.

Mild symptoms in some people: Up to 20 percent of the people who become infected will display symptoms similar to the flu that may include:

• Fever
• Headache
• Body aches
• Nausea
• Vomiting
• Swollen lymph glands
• Skin rash on the chest, stomach and back

Symptoms may only last a few days, though even healthy people have been sick for several weeks.

Serious symptoms in a few people. About one in 150 people infected with West Nile virus will develop severe illness.

The severe symptoms may include:

• High fever
• Headache
• Neck stiffness
• Stupor
• Disorientation
• Coma
• Tremors
• Convulsions
• Muscle weakness
• Vision loss
• Numbness
• Paralysis

West Nile Virus Infection

People typically develop symptoms between three to 14 days after they are bitten by an infected mosquito.

West Nile Virus Treatment

There is not specific treatment for West Nile virus infection. Mild symptoms such as fever and aches usually resolve on their own. 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.

People with mild symptoms do not necessarily need to seek medical attention for this infection. If more severe symptoms develop, such as unusually severe headaches or confusion, seek medical attention immediately. Severe West Nile virus illness usually requires hospitalization.

West Nile Virus Diagnosis

West Nile virus is diagnosed by laboratory confirmation of a blood sample.