St. Louis Encephalitis

What is St. Louis Encephalitis?

St. Louis Encephalitis is a potentially serious viral disease that affects humans, birds, mosquitoes and other animals.

Who gets St. Louis Encephalitis?

Anyone living in an area where virus activity has been identified is at risk of infection with St. Louis Encephalitis.

How does St. Louis Encephalitis spread?

• St. Louis Encephalitis is most often spread by the bite of an infected mosquito.
  • Mosquitoes are St. Louis Encephalitis carriers that become infected when they feed on infected birds.
  • Infected mosquitoes can then spread St. Louis Encephalitis to humans and other animals when they bite.
• St. Louis Encephalitis is not spread from person-to-person.

What are the symptoms of St. Louis Encephalitis?

Most people who are infected with St. Louis Encephalitis have very mild illness or may never become sick. Mild infections are characterized by fever and headache, without other apparent symptoms.

The symptoms of severe disease can include:

• Headache
• High fever
• Neck stiffness
• Confusion
• Coma
• Shaking
• Seizures and/or paralysis

The risk of severe disease increases for those of advanced age.

How soon do infected people get sick?

People typically develop symptoms between 5 and 15 days after they are bitten by an infected mosquito.

How is St. Louis Encephalitis diagnosed?

St. Louis Encephalitis is diagnosed by laboratory confirmation of a blood sample.

How is St. Louis Encephalitis treated?

There is no specific treatment for St. Louis Encephalitis infection. Cases with milder symptoms resolve on their own.

In more severe cases, people usually need to go to the hospital where they can receive supportive treatment.

How can St. Louis Encephalitis infection be prevented?

The easiest and best way to avoid St. Louis Encephalitis is to prevent mosquito bites:

• When you are outdoors, use an insect repellent registered by the Environmental Protection Agency (EPA), such as those containing:
  • DEET (N, N-diethyl-meta-toluamide)
  • Oil of lemon eucalyptus
  • Picaridin
  • Permethrin
  • Follow the directions on the package.
• Wear pants and long-sleeved shirts when outdoors.
• Avoid spending time outside when mosquitoes are most active, notably at dusk (the first two hours after sunset) and dawn.
• Eliminate areas of standing water, including bird baths and un-maintained swimming pools, which support mosquito breeding.
• Make sure doors and windows have tight-fitting screens without tears or holes.

How is St. Louis Encephalitis being addressed in Clark County?

The Southern Nevada Health District Environmental Health Division, in collaboration with the Nevada State Health Division, is conducting surveillance to monitor for St. Louis Encephalitis. There are three categories of surveillance currently underway:

• Dead bird testing (crows, ravens and magpies)
• Mosquito testing
• Sentinel chicken flock testing

To report a dead raven, crow or magpie, contact the Southern Nevada Health District West Nile Hotline at (702) 759-1220. Please note: viable samples can only be collected from birds that have been dead less than 24 hours.

Where can I get more information?

Contact your physician or the Clark County Office of Epidemiology at (702) 759-1300. You may also visit the U.S. Centers for Disease Control and Prevention website at www.cdc.gov/ncidod/dvbid/arbor/sle_ga.htm