Encephalitis: Types, symptoms, causes, and treatment

Encephalitis is an acute inflammation of the brain. The majority of cases are caused by either a viral infection or the immune system mistakenly attacking brain tissue.

In the United States, encephalitis is responsible for an estimated 19,000 hospitalizations, 230,000 hospital days, and $650 million in hospitalization costs.

Around 15 percent of encephalitis cases occur in the HIV-infected population.

In this article, we will look at the symptoms, causes, treatments, and complications of encephalitis.

Fast facts on encephalitis

Here are some key points about encephalitis. More detail and supporting information is in the main article.

Early symptoms are fever, photophobia, and headache

Encephalitis is rarely life-threatening

Encephalitis most often affects children, older adults, and those with compromised immune systems

Only a handful of antiviral medications can help treat encephalitis

Complications of encephalitis can include epilepsy and memory loss

What is encephalitis?

[Brain Illustration]
Encephalitis is an acute inflammation of the brain.

Encephalitis is an acute inflammation (swelling) of the brain usually resulting from either a viral infection or due to the body’s own immune system mistakenly attacking brain tissue.

In medicine, “acute” means it comes on abruptly and develops rapidly; it usually requires urgent care.

The most common cause is a viral infection. The brain becomes inflamed as a result of the body’s attempt to fight off the virus.

Encephalitis occurs in 1 in every 1,000 cases of measles.

Encephalitis generally begins with fever and headache. The symptoms rapidly worsen, and there may be seizures (fits), confusion, drowsiness, and loss of consciousness, and even coma.

Encephalitis can be life-threatening, but this is rare. Mortality depends on a number of factors, including the severity of the disease and age.

Younger patients tend to recover without many ongoing health issues, whereas older patients are at higher risk for complications and mortality.

When there is direct viral infection of the brain or spinal cord, it is called primary encephalitis. Secondary encephalitis refers to an infection which started off elsewhere in the body and then spread to the brain.


Different types of encephalitis have different causes.

Japanese encephalitis is spread by mosquitoes

Tick-borne encephalitis is spread by ticks

Rabies can be spread through a bite from a mammal

There is also primary or secondary encephalitis.

Primary or infectious encephalitis can result if a fungus, virus, or bacterium infects the brain.

Secondary, or post-infectious, encephalitis is when the immune system responds to a previous infection and mistakenly attacks the brain.

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The patient typically has a fever, headache, and photophobia (excessive sensitivity to light). There may also be general weakness and seizures.

Less common symptoms

The individual may also experience nuchal rigidity (neck stiffness), which can lead to a misdiagnosis of meningitis. There may be stiffness of the limbs, slow movements, and clumsiness. The patient may also be drowsy and have a cough.

More serious cases

In more serious cases, the person may experience very severe headaches, nausea, vomiting, confusion, disorientation, memory loss, speech problems, hearing problems, hallucinations, as well as seizures and possibly coma. In some cases, the patient can become aggressive.

Signs and symptoms in infants

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