The Facts About Encephalitis

Encephalitis is irritation and swelling (inflammation) of the brain, usually due to infections. The diseases of major concern in the U.S. for mosquito-borne encephalitis are:

  • Eastern equine encephalitis
  • La Crosse encephalitis
  • St. Louis encephalitis
  • West Nile virus encephalitis
  • Western equine encephalitis
  • Symptoms

When the virus enters the bloodstream, encephalitis causes inflammation of brain tissue and surrounding membranes. White blood cells invade the brain tissue as they try to fight off the infection. The brain tissue swells (cerebral edema), which may destroy nerve cells, cause bleeding in the brain (intracerebral hemorrhage), and brain damage.

Symptoms of vector-borne encephalitis include:

  • Initial mosquito or tick bite
  • Clumsiness
  • Confusion
  • Fever
  • Headache
  • Memory loss
  • Mood changes
  • Muscle weakness
  • Seizures
  • Stiff neck
  • Stupor
  • Vomiting
  • Treatment

No currently available medication “cures” encephalitis. Rather, treatment is supportive, dealing with relieving the associated swelling of the brain, loss of automatic breathing functions and other symptoms or complications.

Tests & Diagnosis – An examination may show:

  • Abnormal reflexes
  • Mental confusion
  • Mouth ulcers
  • Muscle weakness
  • Neck stiffness
  • Signs in other organs, such as the liver and lungs
  • Skin rash
  • Speech problems

Tests may include:

  • Brain MRI
  • CT scan of the head
  • Culture of cerebrospinal fluid (CSF), blood, or urine (however, this test is rarely useful)
  • Electroencephalogram (EEG)
  • Lumbar puncture and CSF examination
  • Tests that detect antibodies to a virus (serology tests)
  • Test that detects tiny amounts of virus DNA (polymerase chain reaction — PCR)

Since encephalitis is caused by a variety of infections, there is no single vaccine for it. Nor is there any commercially available vaccine for many of the initiating pathogens. The U.S. CDC recommends taking preventive measures against mosquito and tick bites.