Encephalitis

Encephalitis is inflammation of the brain. This can develop as a result of infection (usually viral) or when the immune system attacks the tissue of the brain by mistake (post-infectious encephalitis).

Encephalitis usually begins with flu-like symptoms, such as fever and headache. The symptoms rapidly get worse over a short period of time, and a person may experience seizures (fits), changes in mental state, such as confusion, or drowsiness and loss of consciousness, or a coma.

How common is encephalitis?

Encephalitis is rare. In England each year, there are an estimated 1.5 cases of encephalitis for every 100,000 people.

Encephalitis can occur in people of any age, although children under seven and adults over 55 are particularly vulnerable to infection.

In England, the most common cause of encephalitis is the herpes simplex virus (HSV).

Outlook

Encephalitis should be regarded as a medical emergency. Without prompt treatment, a person with encephalitis can suffer life-threatening damage to their brain.

Due to improvements in techniques used for diagnosing encephalitis, plus the introduction of new anti-viral medicines such as aciclovir, survival rates for encephalitis have improved significantly in recent years. There were 55 deaths as a result of encephalitis in England and Wales during 2007.

The damage caused to the brain by encephalitis can result in long-term complications such as:

• memory loss,
• epilepsy, and
• personality and behavioural changes.

Vaccinations

There are a number of vaccinations that protect against some of the viruses that can cause encephalitis.

The mumps, measles and rubella (MMR) vaccine is the best way to protect your child from encephalitis. Before the introduction of the MMR vaccine, measles used to be one of the leading causes of encephalitis in children.

See Prevention, above, for more information about vaccinations.