Symptoms of encephalitis may be mild to begin with, but can become more serious over hours or days.

Occasionally the symptoms may develop gradually over several weeks or even months.

The first symptoms of encephalitis can be similar to flu, such as:

• a high temperature
• a headache
• feeling and being sick
• aching muscles and joints

Some people may also have a spotty or blistery rash on their skin.

But these early symptoms do not always appear and sometimes the first signs of encephalitis may be more serious symptoms.

More severe symptoms develop when the brain is affected, such as:

• confusion or disorientation
• drowsiness
• seizures or fits
• changes in personality and behaviour, such as feeling very agitated
• difficulty speaking
• weakness or loss of movement in some parts of the body
• seeing and hearing things that are not there (hallucinations and hearing voices)
• loss of feeling in certain parts of the body
• uncontrollable eye movements, such as side-to-side eye movement
• eyesight problems
• loss of consciousness

There may also be symptoms of meningitis, such as a severe headache, sensitivity to bright lights, a stiff neck and a spotty rash that does not fade when a glass is pressed against it.

Dial 999 immediately to request an ambulance if you or someone else has serious symptoms of encephalitis.

It's a medical emergency that needs to be seen in hospital as soon as possible.

Read about how encephalitis is diagnosed and how encephalitis is treated.