West Nile virus: What are the long-term health effects?

What are the long-term effects of West Nile virus?

- Alyce / Kentucky

Answer

Because West Nile virus infection is an emerging disease, the long-term effects aren't fully understood.

Most people infected with West Nile virus have no symptoms and no long-term effects. About 20 percent develop a mild infection called West Nile fever, which causes flu-like signs and symptoms — such as fever, muscle aches, headaches and nausea — lasting up to several weeks. Less than 1 percent of infected people develop severe illness, such as encephalitis or meningitis.

Some studies suggest that among people with symptoms severe enough to require hospitalization, one-third to one-half may experience health problems one year later. Another study found that even those with mild illness, such as West Nile fever, may still have health problems after one year. The most common long-term effects of West Nile virus infection include fatigue, memory loss, depression, muscle weakness, headaches and tremors.

It isn't known why some people who develop West Nile virus infection make a complete recovery and others experience ongoing health problems.