Western Equine Encephalitis: Symptoms, Diagnosis, and Treatment

Key points

  • Infection with western equine encephalitis virus can cause a mild febrile illness (fever), but some people can develop more severe disease.
  • Talk with your healthcare provider if you think you or a family member might have western equine encephalitis.
  • There are no specific medicines to treat western equine encephalitis in people.
  • Rest, fluids, and pain medications may relieve some symptoms.
Woman holding her head in pain

Symptoms

No symptoms in most people. Most people infected with western equine encephalitis virus do not develop any symptoms.

Febrile illness (fever) in some people. Some people who are infected develop a fever along with other symptoms, such as headache, body aches, fatigue, or vomiting. Most people with a febrile illness due to western equine encephalitis virus will recover completely within a few days.

Serious symptoms in a few people. Some 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 include high fever, headache, neck stiffness, dizziness, light sensitivity, confusion, agitation, drowsiness, coma, and seizures.
  • Severe illness can occur in people of any age. However, older adults and young children, particularly infants and children aged 2 years and younger, are at greater risk for severe illness.
  • 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.

Diagnosis

Talk with your healthcare provider if you think you or a family member might be infected with western equine encephalitis.

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 of blood or spinal fluid

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

Visit the Healthcare Providers page for information on testing for western equine encephalitis virus.

Treatment

  • No specific medicines are available to treat western equine encephalitis. Antibiotics do not treat viruses.
  • Rest, fluids, and over-the-counter pain medications may relieve some symptoms.
  • In severe cases, patients often need to be hospitalized to receive supportive treatment, such as intravenous fluids, pain medication, and nursing care.

Visit the Healthcare Providers page for information on treatment for western equine encephalitis.

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