Encephalitis Symptoms & Causes in Children

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Contact the Pediatric Neuro-immunology Program

We understand that you may have a lot of questions when your child is diagnosed with encephalitis:

  • What is it?
  • Will my child need to be hospitalized?
  • How will it affect my child long term?

We’ve provided some answers to those questions here, and when you meet with our experts, we can explain your child’s condition and options fully.

What is encephalitis?

Encephalitis simply means that the brain tissues have become inflamed. When brain tissues are inflamed, they don’t work properly, which is why your child may experience seizures, mental confusion or changes in behavior.

Why is encephalitis a concern?

Infection or inflammation in the brain can lead to permanent damage. Unfortunately, there’s no way to predict the long-term effects of encephalitis. Some children have lots of serious symptoms but respond very well to treatment; others have milder cases but have epilepsy and more long-term learning issues.

Why is encephalitis hard to diagnose?

Encephalitis can be hard to diagnose because it’s a reaction to something, in the same way that a bruise is a reaction to an injury. Often, we may find a bruise and not know what caused it; the same is true for encephalitis.

Another reason is that the absolute best way to determine what causes encephalitis is a brain biopsy. But since this is an extremely invasive procedure, it’s usually only used in very severe cases. Instead, we do other tests, such as a spinal tap, which may or may not pick up on a virus in a brain cell.

Can encephalitis be prevented?

Some forms of encephalitis are transmitted through mosquito bites, and we can prevent those forms by preventing mosquito bites. You and your child can help protect yourselves from mosquito bites by:

  • wearing long sleeves, long pants and socks when outside
  • using bug spray
  • wearing light-colored clothing (mosquitoes are attracted to darker colors)
  • avoiding areas of standing water, like ponds, wells and birdbaths (this is where mosquitos lay their eggs)

Causes of Encephalitis

Encephalitis means that the brain tissue has become inflamed, and this can be caused by different things.

  • It can be the normal (and healthy) reaction of the body to a viral or bacterial infection.
  • It can be the immune system over-reacting to an infection that might not even be still present in the body.
  • It can have an auto-immune cause (the body’s immune cells become confused and start to attack healthy tissue), and occur without an infection of any kind.

Where you live might also play a role. For example, in New England, the West Nile virus is the most common mosquito-born viral cause of encephalitis.

1. Viruses and other infectious agents

There are some viruses that we know can cause encephalitis:

  • herpes simplex virus – This is a common cause of encephalitis. Most children have been exposed to this virus, and your child may be infected with it even if she does not have a cold sore or blister around her mouth, or other sign of the virus.
  • enteroviruses – These viruses enter the body through the gastrointestinal tract, and can also cause hand-foot-mouth disease
  • measles, mumps, rubella and chickenpox viruses – Keeping your child up-to-date with her vaccinations greatly lowers the rate of encephalitis from these viruses.

Other times, we may find signs in your child’s blood or spinal fluid (such as an increased white blood cell count) that her body is battling a virus or other infection that may be causing the encephalitis, even if we don’t know which particular one it is.

Encephalitis can also occur following infection by agents carrying diseases, including ticks (Lyme disease), mosquitos (West Nile virus), and cats (Bartonella, otherwise known as “cat-scratch disease”) or other animal exposures, environmental exposure such as swimming in fresh-water bodies, or travel to certain regions.

2. Non-infectious causes

In the past, physicians assumed that if we couldn’t identify the cause of a case of encephalitis, the cause must be a virus that we weren’t able to detect. But now we recognize that encephalitis can also be caused by over-activity of your child’s immune system in a way that may not have been triggered by a virus.

It’s important to remember that the severity of symptoms has nothing to do with the cause, and two people might have equally severe cases of encephalitis caused by different factors.

Symptoms of Encephalitis

Your child’s symptoms may depend on her situation—the part of the brain that is inflamed, the cause of the inflammation, the degree of inflammation, her age and other medical problems she may have. But even children in the same situation may show symptoms differently. Some of the most common symptoms of encephalitis may include:

  • fever
  • headache
  • sensitivity to light
  • neck stiffness
  • skin rashes
  • nausea/vomiting
  • loss of energy/appetite
  • changes in alertness (sleepiness)
  • confusion or hallucinations
  • difficulty talking
  • problems walking
  • seizures

Since encephalitis is often caused by a virus, you may notice symptoms appear alongside or following other symptoms of a virus, such as an upper respiratory infection (like a cold, sore throat), or a gastrointestinal problem like diarrhea, nausea, vomiting or rash.

Frequently Asked Questions (FAQ) about Encephalitis

Q: Will my child be okay?
A: Encephalitis is rarely fatal for children in the United States. It’s impossible to predict how well your child will do, however, since some children with severe cases may do quite well, whereas children with mild cases may have ongoing difficulties with seizures and/or cognitive/behavioral impairments.

Q: Is encephalitis contagious?
A: No, but it may be caused by a contagious virus. If your child catches the same virus that a child with encephalitis caught, she may show the signs of a cold or flu, but it’s unlikely that she’ll develop encephalitis, too.

Q: Can encephalitis be prevented?
A: Sometimes encephalitis can be caused by a mosquito-borne infection, and preventing mosquito bites prevents these types of encephalitis. Consider:

  • wearing long sleeves, long pants and socks when outside
  • using bug spray

Q: Will my child be hospitalized?
A: Most children with encephalitis are hospitalized for at least a couple of days, but some require much longer hospital stays. Here at Boston Children’s, we have a “neurology step-up unit,” where your child can receive additional specialized care from nurses trained in caring for children with neurological disorders if needed after she leaves the emergency room or the intensive care unit, and before she transfers to the general neurology inpatient unit. And after their immediate medical needs are resolved, many children will spend some time in an inpatient rehabilitation facility where they’ll receive intensive therapies such as speech therapy, occupational therapy and physical therapy as needed.

Q: When will we know the full effects of my child’s encephalitis?
A: It’s hard to say because each child and each situation is different. It may take a few months for the brain to heal, although some children recover much more quickly. Generally, once your child’s condition is stabilized, there’s a lot of hope for potential for ongoing improvement. Your child’s outpatient neurologist will follow her closely to monitor this.

Questions to ask your doctor

If your child is diagnosed with encephalitis, you probably have a lot of questions. Lots of parents find it helpful to jot down questions as they arise – that way, when you talk to your child’s doctors, you can be sure that all of your concerns are addressed.


  • Could something other than encephalitis be causing my child’s symptoms?
  • What caused my child’s encephalitis?
  • What is the treatment plan for my child?
  • What signs of an emergency should I watch for, and who should I contact if I see them?
  • What resources are available to help me and my family?

While much remains unknown about this condition, we’ll do everything we can to answer your questions.

- Sandra L. Fenwick, President and CEO

Boston Children's Hospital
300 Longwood Avenue, Boston, MA 02115
For Patients: 617-355-6000