Definition

Western equine encephalitis (WEE) is a virus spread by a bite from an infected mosquito. While WEE is rare, an infected person can become seriously ill and even die from the virus.

Causes

WEE is caused by being bitten by a mosquito that is infected with the virus.

Risk Factors

Factors that may increase your risk of WEE include:

• Living in or visiting the plains regions of western and central United States
• Doing activities outdoors and not using insect repellent

Symptoms

Most people with WEE do not have any symptoms.

If symptoms do occur, they appear within 5-10 days after infection and include:

• Headache
• Fever
• Neck stiffness
• Chills
• Fatigue
• Joint and muscle pain
• Vomiting

Diagnosis

In addition to taking your medical history and doing a physical exam, your doctor will ask you:

• What kind of symptoms you are experiencing
• Where you have been living or traveling
• Whether you have been exposed to mosquitoes

Your doctor may need to test your bodily fluids. This can be done with:

Treatment

Because the infection is viral, there is no specific treatment for WEE. Treatment will focus on managing your symptoms and related complications through:

Prevention

There is no vaccine for humans. There is a vaccine for horses. Prevention of WEE focuses on controlling mosquitoes and avoiding mosquito bites. Steps you can take to avoid mosquito bites include:

• Stay inside between dusk and dark, when mosquitoes are most active.
• Wear long pants and long-sleeved shirts when outside.
• Use an insect repellent with DEET.
• Repair screens to prevent mosquitoes from entering the house.
• Remove standing water (eg, bird baths, clogged gutters) to prevent mosquito breeding.