Western Equine Encephalitis Clinical Presentation

Updated: Mar 15, 2019
  • Author: Mohan Nandalur, MD; Chief Editor: Michael Stuart Bronze, MD  more...
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Western equine encephalitis (WEE) is difficult to diagnose because of the lack of specificity in symptoms. Often, the goal in these situations is to determine the extent of the patient's illness and whether treatable CNS infection is a possibility. Most patients commonly present with the initial signs and symptoms of a viral prodrome. The prodromal phase is often short, averaging 1-4 days, and consists of fever, headache, chills, nausea, and vomiting. In many patients, especially adults, the disease may be subclinical, and these patients may never develop symptoms beyond that of the viral prodrome. Physicians must have a heightened awareness for neurologic symptoms and sequelae, especially in younger patients.

Once neurologic symptoms arise, patients have a poorer prognosis and decompensate rapidly. Neurologic symptoms may include the following:

  • Headache - Often the most prevalent symptom

  • Nausea or vomiting - Present in the prodromal and active stages of illness

  • Confusion

  • Focal neurologic deficits (ie, sensory or motor loss in 1 distribution) - Low prevalence

  • Seizures (most commonly of the general tonic-clonic or partial complex) - Greater frequency in very young children

  • Somnolence

  • Neck stiffness

  • Malaise and weakness

  • Cranial nerve palsies (rare)

  • Photophobia

Other associated symptoms may include the following:

  • Vertigo (common)

  • Abrupt fever - Almost invariably present at some point

  • Chills

  • Abdominal pain

  • Diarrhea

  • Sore throat (common)

  • Arthralgias or myalgias

  • Respiratory difficulty (common)

Social history may include the following:

  • Recent travel to endemic areas

  • Pertinent outdoor exposure history

  • Work related to the care of horses

  • Recent insect bites

  • Recent illnesses

  • Recent ill contacts

  • Pertinent home and work locations


Physical Examination

The findings on physical examination also are nonspecific and are similar to findings of many other encephalitides.

Changes in vital signs may include the following:

  • Fever

  • Tachycardia

  • Possibly tachypneic

Neurologic findings may include the following:

  • Bilateral papilledema

  • Nuchal rigidity

  • Focal sensory or motor deficit

  • Depressed or hyperactive reflexes

  • Tremors

  • Fasciculations

  • Seizure activity

  • Spastic paralysis

Other findings may include the following:

  • Cyanosis, if respiratory compromise is present

  • Facial, periorbital, or generalized edema

  • Lymphadenopathy (not necessarily present)

  • Possible pharyngeal erythema

  • Infants - Bulging fontanelles (possibly)