What Is West Nile Virus? West Nile virus (WNV) is a potentially
serious illness. Experts believe WNV is established as a
seasonal epidemic in North America that flares up in the summer
and continues into the fall. This fact sheet contains important
information that can help you recognize and prevent West Nile
virus. What Are the Symptoms of WNV? WNV affects the central
nervous system. Symptoms vary. - No Symptoms in Most People.
Approximately 80 percent of people who are infected with WNV
will not show any symptoms at all. - Mild Symptoms in Some
People. Up to 20 percent of the people who become infected will
display mild symptoms, including fever, headache, and body
aches, nausea, vomiting, and sometimes swollen lymph glands or a
skin rash on the chest, stomach and back. Symptoms typically
last a few days. - Serious Symptoms in a Few People. About one
in 150 people infected with WNV will develop severe illness. The
severe symptoms can include high fever, headache, neck
stiffness, stupor, disorientation, coma