Definition

Western equine encephalitis (WEE) is an infection from a mosquito. WEE is rare. It can range from mild to severe or fatal.

Causes

WEE is caused by a virus. It is spread to humans from the bite of an infected mosquito. The virus is not spread from person to person.

Risk Factors

Things that may raise the risk of WEE are:

• Living in or visiting the plains region of western and central US
• Being outdoors
• Not using bug spray

Symptoms

Most people with WEE do not have any symptoms.

If symptoms do happen, they may be:

• Headache
• Fever and chills
• Nausea and vomiting
• Neck stiffness
• Feeling tired
• Joint and muscle pain

WEE can lead to more serious, life-threatening symptoms. These may include inflammation of the brain (encephalitis), seizures, and coma. Serious symptoms are more common in infants and older adults.

Diagnosis

The doctor will ask about your symptoms, travel, and health history. A physical exam will be done.

Tests may be done to diagnose the infection. They may be:

• Blood tests
• Lumbar puncture—some fluid around the brain and spinal cord is taken and tested

Imaging tests may be done to check the brain. They may include:

• MRI scan
• CT scan

Treatment

There is no specific treatment for WEE. Treatment depends on how severe the disease is. The goal is to manage symptoms and problems. In severe cases, hospital care is needed.

Depending on the symptoms, options may be:

• IV fluids
• Antiseizure medicines
• Medicines to decrease brain swelling
• Mechanical ventilation

Prevention

WEE can be prevented by avoiding mosquito bites. Things that may help are:

• Covering up the skin
• Using bug sprays, netting, and screens
• Staying indoors between dusk and dark