What is Western equine encephalitis (WEE)?

Western equine encephalitis (WEE) is a mosquito-borne virus that can make horses and humans sick and in some cases cause death. The term encephalitis refers to an inflammation of the brain; encephalomyelitis refers to an inflammation of the brain and spinal cord.

How is WEE transmitted?

Humans and horses acquire WEE from the bite of an infected mosquito. The mosquito becomes infected with the virus after biting a bird infected with WEE.

Who is at risk of being infected with St. Louis encephalitis?

People who spend time outdoors when SLEV infected mosquitoes are active, such as at dawn and dusk, are at increased risk.

What are the symptoms of WEE in humans?

Symptoms of these diseases develop within 5 to 15 days after the bite of an infected mosquito. Initial symptoms often resemble the flu with fever and headache being most common. Severe cases can result in disorientation, coma, and even death.

What can a person do to prevent WEE ?

• Apply insect repellent containing DEET, picaridin, IR3535, or oil of lemon eucalyptus on exposed skin and clothing before spending time outside.
• Wear long sleeves and pants when mosquitoes are biting.
• Keep screens on windows and doors in good repair.
• Reduce mosquito production by identifying and eliminating standing water around your home in containers such as flower pots, tires, rain barrels, bird baths, and children’s toys.
• Contact the District at 707-285-2200 if you detect unusually high numbers of mosquitoes.
• Horse owners should consult their vetrinarian to discuss vaccination options.