St. Louis Encephalitis: A Mosquito-Borne Virus

A Culex mosquito on human skin. Image from CDC's page.

St. Louis encephalitis is caused by a virus spread by infected mosquitoes. The number of cases each year varies widely. Most U.S. cases occur in eastern and central states, though sporadic cases and outbreaks have also occurred in the Southwest.

Symptoms

Most people infected have no symptoms. Those who get sick may have:

• fever
• headache
• nausea and vomiting
• tiredness

Some develop severe neuroinvasive disease, such as encephalitis (inflammation of the brain) or meningitis (inflammation of the membranes around the brain and spinal cord).

How it spreads

The virus reaches people through the bites of infected mosquitoes.

Prevention

There are no vaccines or medicines to prevent St. Louis encephalitis. The way to lower your risk is to prevent mosquito bites.

Testing and treatment

• See a health care provider if you develop symptoms after being exposed to mosquitoes where the virus spreads.
• There is no specific treatment, and antibiotics don't work against viruses. Rest, fluids and over-the-counter pain medicine may ease some symptoms.
• In severe cases, patients often need hospital care — such as IV fluids, pain medicine and nursing care.

Sources

Based on "About St. Louis Encephalitis Virus," Centers for Disease Control and Prevention; a work of the United States government in the public domain.