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What is encephalitis?

Encephalitis is an acute brain inflammation. Most cases are caused either by a viral infection, or by an erroneous attack on brain tissue by the immune system.

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

In the HIV-infected population, around 15 per cent of cases of encephalitis occur. 

In this post, we’ll look at the encephalitis signs, causes, remedies, and complications.

Important facts about encephalitis

Here are a few key points about encephalitis. The main article includes more descriptions and supporting material.

  • 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
brain-illusEncephalitis is an acute inflammation of the brain.tration

Encephalitis is an acute brain inflammation (swelling) that is usually caused either by a viral infection or by the body’s own immune system which mistakenly attacks brain tissue.

“Acute” in medicine means that it occurs suddenly and progresses rapidly; this typically requires immediate treatment.

A Viral Infection is the most common cause. Regardless of the body’s effort to fend off the infection the brain is inflamed.

Encephalitis occurs in one of every one thousand measles cases.

Commonly, encephalitis starts with fever and headache. The symptoms escalate rapidly, and seizures (fits), confusion, drowsiness, and loss of consciousness, and even coma, can occur.

Encephalitis is potentially life-threatening, although that is rare. Mortality relies on a variety of factors, including disease severity and age.

Younger patients continue to recover without many ongoing health problems while older patients are at higher risk of complications and mortality.

If the brain or spinal cord has direct viral infection it is called primary encephalitis. Secondary encephalitis refers to an infection which began somewhere else 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 occur if the brain is infected by a fungus, virus or bacterium.

Secondary or post-infectious encephalitis occurs when a previous infection occurs responded to by the immune system and the brain is wrongly targeted.


The patient usually has an extreme sensitivity to light (fever, headache, and photophobia). General weakness and seizures can also occur.

Less common symptoms

Individuals may also experience nuchal rigidity (neck stiffness), which may cause meningitis to be misdiagnosed. The limbs can be rigid, slow motion, and clumsiness. Sometimes, the patient may be drowsy and have a cough.

More serious cases

The person can suffer very severe headaches, nausea, vomiting, confusion, disorientation, memory loss, speech problems, hearing problems, hallucinations, as well as seizures and possibly coma, in more serious cases. The patient can become violent, in some cases.

Signs and symptoms in infants

Initially, it is difficult to diagnose encephalitis in young children and babies. Parents or guardians will watch for vomiting, a bulging fontanel (the soft area at the top of the head centre), incessant crying that doesn’t get better when the baby is picked up and comforted, and body stiffness.


Encephalitis may develop as a result of a direct infection of a virus, bacterium, or fungus in the brain, or when the immune system responds to an earlier infection; the immune system erroneously attacks brain tissue.

Primary (infectious) encephalitis can be split into three main categories of viruses:

  1. Common viruses, including HSV (herpes simplex virus) and EBV (Epstein-Barr virus)
  2. Childhood viruses, including measles and mumps
  3. Arboviruses (spread by mosquitoes, ticks, and other insects), including Japanese encephalitis, West Nile encephalitis, and tick-borne encephalitis

Secondary encephalitis: a complication of a viral infection may cause it. Symptoms tend to occur days after initial infection, or even weeks after. The patient’s immune system treats and attacks healthy brain cells as foreign organisms. We still do not know why this would cause the immune system to malfunction.

The exact cause of the disease is not tracked in more than 50 percent of cases of encephalitis.

Encephalitis is more likely to affect infants, older adults, people with weakened immune systems, and people living in areas where mosquitoes and ticks are common that transmit particular viruses.


Encephalitis therapy is aimed at alleviating the symptoms. There are only a small number of consistently tested effective antiviral agents that can aid, one of which is acyclovir; efficacy is minimal for most infections except when herpes simplex is the cause of the disease.

Corticosteroids can be given to reduce inflammation of the brain, especially in cases of post-infectious (secondary) encephalitis. If the patient has serious symptoms, mechanical ventilation may be required to help them breathe, as well as other supportive care.

Patients that have seizures are often given anticonvulsants. Sedatives may be helpful for seizures, irritability and restlessness. In patients with moderate symptoms the only treatment for fever and headaches is rest, plenty of fluids, and Tylenol (paracetamol).


MRI image scan
Diagnosis of encephalitis can be challenging.

Doctors that recognise the classic adult symptoms — fever, headache, confusion, and occasionally seizures, or irritability, poor appetite, and fever in young children — can prescribe additional diagnostic tests.

As a general rule, a neurological examination finds the patient confused and drowsy.

The doctor may suggests a diagnosis of meningitis or meningoencephalitis if the neck is stiff, caused by irritation of the meninges (membranes that cover the brain and spinal cord).

A lumbar puncture that takes a sample of cerebrospinal fluid from the spine can show higher levels of protein and white blood cells than normal.

Nonetheless, this check is not always conclusive; in some cases, even if the patient has encephalitis, the findings can return normal.

A CT scan can be useful for detecting brain structural changes. This may also rule out other causes including stroke, an aneurysm or a tumor. Nonetheless, the best imaging method for encephalitis is an MRI; it will recognize the classical changes in the brain that indicate encephalitis.

An EEG (electroencephalograph) measuring the brain’s electrical activity may be displaying rapid waves in one or both of the temporal lobes in encephalitis patients.

If the cause is thought to be a West Nile virus infection, the doctor may order a blood test.


Most encephalitis patients tend to have at least one complication, particularly the elderly patients, those with coma symptoms, and individuals who did not receive early care.

Complications may include:

  • Loss of memory – especially among those who had herpes simplex virus encephalitis
  • Behavioral or personality changes – such as mood swings, bouts of frustration and anger, and anxiety
  • Epilepsy
  • Aphasia – language and speech problems


Holding the vaccines up-to-date is the most successful way to reduce the risk of contracting encephalitis. Can include measles, mumps, rubella vaccines and Japanese encephalitis and tick-borne encephalitis, if the virus occurs in those regions.

Individuals should take measures to reduce the risk of biting in areas known to have mosquitoes that carry encephalitis-causing viruses. This may include wearing suitable clothing, avoiding mosquito-infested areas, avoiding outdoors at specific times during the day when there are large numbers of mosquitoes around, keeping the home mosquito-free, using mosquito repellent, and ensuring that there is no stagnant water around the home.

Chukwuebuka Martins

Chukwuebuka Martins is a writer, researcher, and health enthusiast who specializes in human physiology. He takes great pleasure in penning informative articles on many aspects of physical wellness, which he then thoroughly enjoys sharing to the general public.