Symptoms of Western Equine Encephalitis

For Everyone

Key points

  • Infection with western equine encephalitis virus can cause a mild febrile illness, but some people can develop more severe illness.
  • Talk to your healthcare provider if you think you or a family member might have western equine encephalitis.
Woman holds her head in pain.

Symptoms

Most people infected with western equine encephalitis virus do not develop any symptoms. For people with symptoms, the time from mosquito bite to feeling sick (incubation period) ranges from 5 to 10 days.

Mild illness

Some people who are infected develop symptoms including:

  • Fever
  • Headache
  • Body aches
  • Fatigue
  • Vomiting

Most people with a febrile illness due to western equine encephalitis virus will recover completely within a few days.

Severe illness

A few people who are infected develop a severe illness affecting the central nervous system such as encephalitis (inflammation of the brain), myelitis (inflammation of the spinal cord), or meningitis (inflammation of the membranes that surround the brain and spinal cord).

Symptoms of severe illness can include:

  • High fever
  • Headache
  • Neck stiffness
  • Dizziness
  • Light sensitivity
  • Confusion
  • Agitation
  • Drowsiness
  • Coma
  • Seizures

Treatment

No medicines are available to treat western equine encephalitis. Rest, fluids, and over-the-counter pain medications may relieve some symptoms.

Outcomes and complications

Recovery from severe illness might take several weeks or months. Some effects to the central nervous system might be permanent and are more common in infants and young children.

About 3 to 15 out of 100 people with severe disease will die.

For Health Care Providers Clinical Features, Diagnosis, and Treatment of Western Equine Encephalitis

Risk factors

Severe illness can occur in people of any age. However, some people are at greater risk for severe illness including:

Testing and diagnosis

If you think you or a family member might have western equine encephalitis, talk to your healthcare provider.

Healthcare providers diagnose western equine encephalitis virus infection based on:

  • Signs and symptoms
  • History of possible exposure to mosquitoes that can spread western equine encephalitis virus
  • Laboratory testing

Your healthcare providers can order tests to look for western equine encephalitis virus or other infections that can cause similar symptoms.

Print
Content Source:
National Center for Emerging and Zoonotic Infectious Diseases (NCEZID)