Encephalitis (en-sef-uh-LIE-tis) is inflammation of the brain. Viral infections are the most common cause of the condition.

Encephalitis can cause flu-like symptoms, such as a fever or severe headache. It can also cause confused thinking, seizures, or problems with senses or movement. However, many cases of encephalitis result in only mild flu-like symptoms or even no symptoms.

Severe cases of encephalitis, while relatively rare, can be life-threatening. Because the course of any single case of encephalitis can be unpredictable, it's important to get a timely diagnosis and treatment.

Symptoms Causes Risk factors Complications Prevention

Most people with viral encephalitis have either no symptoms or mild flu-like symptoms, such as the following:

  • Headache
  • Fever
  • Aches in muscles or joints
  • Fatigue or weakness

More-serious cases require prompt medical care. Additional signs and symptoms of more serious encephalitis may include the following:

  • Confusion, agitation or hallucinations
  • Seizures
  • Loss of sensation or paralysis in certain areas of the face or body
  • Muscle weakness
  • Double vision
  • Perception of foul smells, such as burned meat or rotten eggs
  • Problems with speech or hearing
  • Loss of consciousness

Signs and symptoms in infants and young children may also include:

  • Bulging in the soft spots (fontanels) of the skull in infants
  • Nausea and vomiting
  • Body stiffness
  • Inconsolable crying
  • Poor feeding or not waking for a feeding
  • Irritability

When to see a doctor

Get immediate care if you or someone you know is experiencing any of the symptoms associated with more-severe cases of encephalitis. Severe headache, fever and altered consciousness require urgent care.

Infants and young children with any signs or symptoms of encephalitis should receive urgent care.

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