Symptoms of encephalitis 

The symptoms of encephalitis are initially mild, but they can quickly become more serious.

Encephalitis usually begins with flu-like symptoms, such as:

  • high temperature (fever) of 38C (100.4F) or above
  • headache 
  • nausea and vomiting
  • joint pain

After this initial stage, more serious symptoms can begin to develop within hours or days, which may include:

  • changes in mental state, such as confusion, drowsiness or disorientation
  • seizures (fits)
  • changes in personality and behaviour
  • loss of consciousness

Flu-like symptoms that rapidly get worse and affect a person's mental state should be treated as a medical emergency. Dial 999 immediately to request an ambulance.

Other symptoms of encephalitis can include:

  • sensitivity to bright lights (photophobia)
  • inability to speak
  • inability to control physical movements
  • stiff neck
  • hallucinations (seeing and hearing things that aren't there)
  • loss of sensation in certain parts of the body
  • partial or total vision loss
  • involuntary eye movements, such as side-to-side eye movement

A rash may develop if the infection is caused by a particular virus. For example, if the herpes simplex virus is responsible for the infection, you may have the characteristic blisters on your skin, eyes or mouth.

Page last reviewed: 16/12/2014

Next review due: 16/12/2016