West Nile Virus (WNV) can affect the central nervous system. The severity of symptoms can vary from person to person.
- No symptom in most people: Approximately 80 percent of people who are infected with WNV will not show any symptoms and will not know they have it.
- Mild infection in some people: Up to 20 percent of the people who become infected will display mild flu-like symptoms, including headache and body aches, nausea, vomiting, as well as swollen lymph glands, or a skin rash on the chest, stomach, and back. Symptoms typically last a few days. This is known as West Nile Fever.
- Serious infection in a few people: About one in 150 people infected with WNV will develop severe illness, such as West Nile Encephalitis, West Nile Meningitis, or West Nile Meningoencephalitis. The symptoms can include headache as well as neck stiffness, confusion, and high fever. These symptoms may last several weeks or even months. The neurological effects may be permanent.
- WNV is known to cause death in rare circumstances.