Project Description

Encephalitis Fast Facts

Up to 60% of all cases of encephalitis go undiagnosed. The CDC documents several thousand cases of encephalitis in the United States each year but estimates that many more cases go unreported because symptoms are mild or non-existent.

About 175 cases of herpes simplex encephalitis (HSE) occur each year in the United States, accounting for about 10% of all encephalitis cases. When left untreated, the fatality rate of HSE is more than 50%. HSE is most common in adults between the ages of 20 and 40.

Eastern equine encephalitis usually affects fewer than 10 people in the United States each year, but the fatality rate for the disease can be as high as 30%.

The most common cause of encephalitis is an infection by one of several types of viruses, some of which are spread by the bite of infected insects or ticks.

What is Encephalitis?

Encephalitis is inflammation and swelling of brain tissue. Although the symptoms in most cases are mild, the condition can cause significant impairment of brain function.

The most common cause of encephalitis is an infection by one of several types of viruses, some of which are spread by the bite of infected insects or ticks. Bacterial infections and inflammatory conditions can also sometimes cause encephalitis, and one type of the disease is caused by an abnormal reaction of the body’s own immune system.

In many cases, encephalitis produces no symptoms at all, and in mild cases, the symptoms often resemble those of the flu, including fever, body aches, fatigue, and headache.

Other common encephalitis symptoms include:

  • Stiff neck
  • Light sensitivity
  • Irritability, moodiness, or personality changes
  • Fatigue, lethargy, or sleepiness
  • Loss of appetite
  • Balance problems
  • Nausea or vomiting
  • Seizures

In more severe cases, symptoms can include weakness or paralysis of limbs and problems with speech, vision, or hearing.

*The medical information we gather and publish is vetted and intended to be up to date, accurate and express a spectrum of recognized scientific and medical points of view. The information comes from a nucleus of informed scientists, medical doctors, peer-reviewed scientific journals and the National Institute of Health. Please note, differing points of view among scientists and physicians are common. Every effort is employed to ensure the accuracy of these different points of view. That notwithstanding, it is incumbent on persons using this information to consult with his/her physician before reaching any conclusions. Our medical information and publications are not intended to be a substitute for consultation with one’s physician.

What Causes Encephalitis?

Very often, encephalitis is a result of a viral infection that directly affects the brain, causing inflammation and swelling. These types of the disease are called primary encephalitis, and they are often transmitted to humans by the bite of a tick, insect, or another animal that is infected with the virus.

Types of viral encephalitis include:

  • Herpes simplex encephalitis (HSE) is caused by the herpes simplex virus types 1 and 2, and the brain inflammation may result from reactivation of a virus that was already present and inactive in the body. Herpes simplex virus type 1 causes cold sores and is commonly acquired in childhood. The type 2 virus is usually spread through sexual contact. HSE is rare but is potentially very serious or even fatal.
  • Mosquito-born viral encephalitis types include Eastern equine encephalitis, Western equine encephalitis, West Nile encephalitis, La Crosse encephalitis, and St. Louis encephalitis. These types usually cause flu-like symptoms within days or weeks after the mosquito bite.
  • Tick-borne viral encephalitis includes Powassan encephalitis, which produces symptoms within 7-10 days after the bite of an infected tick.
  • Rabies virus is transmitted through a bite or scratch from an infected animal, and symptoms rapidly progress to severe encephalitis. Cases of rabies are rare in the United States, but if left untreated, the disease is almost always fatal.
  • Bacterial or protozoan infections such as toxoplasmosis or malaria may also be a cause.

Sometimes encephalitis is caused by the body’s immune system as it tries to fight off another infection. In this case, the immune system mistakes proteins in nerve cells with those in a virus, causing the immune system to attack the healthy nerve cells. This type of encephalitis is called secondary encephalitis, post-infection encephalitis, or autoimmune encephalitis.

Infections that may trigger autoimmune encephalitis include:

  • Enterovirus infections
  • Epstein-Barr virus
  • Hepatitis A or B
  • Influenza
  • Human immunodeficiency virus (HIV)
  • Childhood diseases such as measles, mumps, and rubella
  • Cancer

Another form of autoimmune encephalitis occurs when the immune system attacks nerve-cell proteins called N-methyl-d-aspartate (NMDA) receptors. Called anti-NMDA receptor encephalitis, this type of the disease sometimes follows cases of herpes simplex encephalitis

*The medical information we gather and publish is vetted and intended to be up to date, accurate and express a spectrum of recognized scientific and medical points of view. The information comes from a nucleus of informed scientists, medical doctors, peer-reviewed scientific journals and the National Institute of Health. Please note, differing points of view among scientists and physicians are common. Every effort is employed to ensure the accuracy of these different points of view. That notwithstanding, it is incumbent on persons using this information to consult with his/her physician before reaching any conclusions. Our medical information and publications are not intended to be a substitute for consultation with one’s physician.

Is Encephalitis Hereditary?

In general, there seems to be little connection between family health history and the development of encephalitis. One study, however, has suggested that susceptibility to one type of encephalitis might come from a deficiency in a particular gene, and that deficiency might be inherited within families.

In 2006, researchers in France found that some otherwise healthy patients had an inability to produce a protein that helps the immune system to recognize viruses and other pathogens. The lack of this protein made the patients’ cells vulnerable to herpes simplex type 1 infections.

The researchers suggested that this vulnerability could lead to an increased risk of developing herpes simplex encephalitis. Further, they suggested that the gene mutation that causes protein deficiency could be inherited, rather than being caused by external environmental factors.

*The medical information we gather and publish is vetted and intended to be up to date, accurate and express a spectrum of recognized scientific and medical points of view. The information comes from a nucleus of informed scientists, medical doctors, peer-reviewed scientific journals and the National Institute of Health. Please note, differing points of view among scientists and physicians are common. Every effort is employed to ensure the accuracy of these different points of view. That notwithstanding, it is incumbent on persons using this information to consult with his/her physician before reaching any conclusions. Our medical information and publications are not intended to be a substitute for consultation with one’s physician.

How Is Encephalitis Detected?

Early detection, diagnosis, and treatment of encephalitis are important. Although many cases are relatively mild and may resolve on their own, severe cases of encephalitis–and especially types like herpes simplex encephalitis and eastern equine encephalitis–are likely to cause long-term harm or even death if left untreated and allowed to progress.

Early signs of encephalitis, which often precede the more commonly recognized symptoms, include:

  • Nausea or vomiting
  • Abdominal pain
  • Diarrhea
  • Cough
  • Sore throat
  • Runny nose
  • Body aches
  • Fever
  • Swollen lymph nodes

As encephalitis progresses, other more profound symptoms usually emerge, such as:

  • Headache
  • Confusion or disorientation
  • Irritability or mood changes
  • Numbness or paralysis in limbs
  • Seizures
  • Unusual sleepiness or fatigue

You should see a doctor immediately if you experience severe symptoms such as high fever, intense headache, or pronounced confusion. Children who exhibit any symptoms should also see a doctor immediately.

*The medical information we gather and publish is vetted and intended to be up to date, accurate and express a spectrum of recognized scientific and medical points of view. The information comes from a nucleus of informed scientists, medical doctors, peer-reviewed scientific journals and the National Institute of Health. Please note, differing points of view among scientists and physicians are common. Every effort is employed to ensure the accuracy of these different points of view. That notwithstanding, it is incumbent on persons using this information to consult with his/her physician before reaching any conclusions. Our medical information and publications are not intended to be a substitute for consultation with one’s physician.

How Is Encephalitis Diagnosed?

If you exhibit symptoms consistent with encephalitis, your healthcare provider will move through a series of diagnostic steps to see if you have the condition.

  • Physical exam and medical history. The doctor will look for signs that you may be at risk for encephalitis. He or she may ask if you’ve recently had a gastrointestinal or respiratory illness (cold or flu), if you’ve been at risk for a tick or mosquito bite, or if you’ve recently traveled to areas where encephalitis is known to be prevalent.
  • Laboratory tests. Tests of your blood, urine, stool, and throat cultures can determine whether or not there is an infection in your body that could lead to encephalitis.
  • Electroencephalogram (EEG). This test monitors your brain’s electrical activity and can help to detect abnormalities in brain function.
  • Imaging tests. Magnetic resonance imaging (MRI) and computed tomography (CT) scans can detect brain swelling caused by encephalitis. These tests may also rule out encephalitis by revealing another condition that’s causing your symptoms.
  • Spinal tap. This procedure removes and tests a small amount of the fluid that protects your brain and spinal column. The test can often detect viral infections or inflammation in the brain.
  • Brain biopsy. This test, in which a small amount of brain tissue is removed and tested, is rarely used to diagnose encephalitis, but it may be necessary if the condition does not respond to initial treatment.

*The medical information we gather and publish is vetted and intended to be up to date, accurate and express a spectrum of recognized scientific and medical points of view. The information comes from a nucleus of informed scientists, medical doctors, peer-reviewed scientific journals and the National Institute of Health. Please note, differing points of view among scientists and physicians are common. Every effort is employed to ensure the accuracy of these different points of view. That notwithstanding, it is incumbent on persons using this information to consult with his/her physician before reaching any conclusions. Our medical information and publications are not intended to be a substitute for consultation with one’s physician.

How Is Encephalitis Treated?

Treatment for encephalitis involves both controlling the inflammation and swelling of the brain, which can cause long-term damage and death, and treating the underlying infection or immune system problem that caused the encephalitis in the first place.

Treatment for mild cases of encephalitis typically includes:

  • Bed rest
  • Sufficient hydration
  • Over-the-counter anti-inflammatory medications such as acetaminophen, ibuprofen, or naproxen sodium

When encephalitis symptoms are severe and require hospitalization, more advanced treatments can include:

  • Intravenous hydration
  • Mechanical breathing assistance
  • More aggressive anti-inflammatory medications such as corticosteroids
  • Anticonvulsant medications to treat seizures

The infections that cause viral encephalitis can be treated with anti-viral drugs such as:

  • Acyclovir to treat the herpes simplex or chickenpox (varicella-zoster) virus
  • Ganciclovir or foscarnet to treat cytomegalovirus
  • Antiretroviral medications to treat HIV-related encephalitis

Bacterial infections may be treated with antibiotics.

Autoimmune encephalitis is often treated with corticosteroids such as prednisone or methylprednisolone. Other approaches include transfusions of blood plasma to remove abnormal antibodies or the intravenous administration of normal antibodies.

*The medical information we gather and publish is vetted and intended to be up to date, accurate and express a spectrum of recognized scientific and medical points of view. The information comes from a nucleus of informed scientists, medical doctors, peer-reviewed scientific journals and the National Institute of Health. Please note, differing points of view among scientists and physicians are common. Every effort is employed to ensure the accuracy of these different points of view. That notwithstanding, it is incumbent on persons using this information to consult with his/her physician before reaching any conclusions. Our medical information and publications are not intended to be a substitute for consultation with one’s physician.

How Does Encephalitis Progress?

Encephalitis may become a severe health threat depending on its cause, the severity of the initial infection, and the length of time that the condition goes untreated. Especially young or elderly patients are at the greatest risk of developing life-threatening complications.

With treatment, mild cases of encephalitis usually resolve within a few weeks and don’t cause long-term or permanent complications. Severe cases, however, may produce permanent complications, and the worst cases can result in coma or death.

Long-term or permanent complications may include:

  • Concentration or mental focus difficulties
  • Memory loss
  • Fatigue or weakness
  • Irritability or personality changes
  • Seizures
  • Paralysis
  • Problems with speech, hearing, or vision

*The medical information we gather and publish is vetted and intended to be up to date, accurate and express a spectrum of recognized scientific and medical points of view. The information comes from a nucleus of informed scientists, medical doctors, peer-reviewed scientific journals and the National Institute of Health. Please note, differing points of view among scientists and physicians are common. Every effort is employed to ensure the accuracy of these different points of view. That notwithstanding, it is incumbent on persons using this information to consult with his/her physician before reaching any conclusions. Our medical information and publications are not intended to be a substitute for consultation with one’s physician.

How Is Encephalitis Prevented?

The best prevention strategy for encephalitis is avoiding the infections that may cause the condition.

To protect yourself from the common viruses that cause encephalitis, take these steps:

  • Vaccinate yourself and your children against common viruses such as measles, mumps, rubella, and chickenpox. If you’re traveling to foreign destinations, ask your doctor if you need vaccinations against locally prevalent viruses, bacteria, or protozoa.
  • Wash your hands and practice good hygiene to prevent the spread of viruses. Teach your children these practices, too.
  • Don’t share utensils, food, or beverages.

To guard against tick- or mosquito-borne encephalitis, these precautions are recommended:

  • Wear long sleeves and long pants when you’re outside, especially in areas of tall grass and between dusk and dawn.
  • Use insect repellents and insecticides.
  • Avoid wet areas where mosquitoes are common and don’t allow standing water to collect around your home.

*The medical information we gather and publish is vetted and intended to be up to date, accurate and express a spectrum of recognized scientific and medical points of view. The information comes from a nucleus of informed scientists, medical doctors, peer-reviewed scientific journals and the National Institute of Health. Please note, differing points of view among scientists and physicians are common. Every effort is employed to ensure the accuracy of these different points of view. That notwithstanding, it is incumbent on persons using this information to consult with his/her physician before reaching any conclusions. Our medical information and publications are not intended to be a substitute for consultation with one’s physician.

Encephalitis Caregiver Tips

After surviving a severe case of encephalitis, patients are very often forced to deal with complications that may last the rest of their lives. Although the disease is gone, its lingering effects can make everyday difficult, and caregivers can help sufferers to return to their normal daily routines as much as possible.

  • Learn as much as you can about the disease and its long-term effects. The sufferer may need help with ongoing therapies, such as physical therapy, occupational therapy, speech therapy, or psychotherapy.
  • Understand that although your loved one may look as if everything is fine, he or she may be struggling with subtle, unseen complications. Depression and anxiety often are a result of these struggles, and daily tasks such as paying bills may be difficult, a situation that can lead to financial missteps. As a caregiver, be aware that these apparently unrelated problems are a result of the disease and be alert for warning signs.
  • Create an environment that’s free of distraction and confusion to help the sufferer cope with any problems with concentration or focus.
  • Find a support group for both the sufferer and yourself as a caregiver. It always helps to know that you’re not alone in what you’re going through.

*The medical information we gather and publish is vetted and intended to be up to date, accurate and express a spectrum of recognized scientific and medical points of view. The information comes from a nucleus of informed scientists, medical doctors, peer-reviewed scientific journals and the National Institute of Health. Please note, differing points of view among scientists and physicians are common. Every effort is employed to ensure the accuracy of these different points of view. That notwithstanding, it is incumbent on persons using this information to consult with his/her physician before reaching any conclusions. Our medical information and publications are not intended to be a substitute for consultation with one’s physician.

Encephalitis Brain Science

Encephalitis research includes studies aimed at finding ways to prevent or cure the infections that cause the condition, effective ways to treat the condition when it occurs, and ways to better help patients to recover from the effects of encephalitis over the long term.

One current study is examining the early symptoms of anti-NMDA receptor encephalitis, specifically psychiatric and speech symptoms that occur in the early phases of the condition. These early symptoms often progress to more severe symptoms such as seizures and movement abnormalities. The study hopes to help practitioners better recognize the very early signs so that treatment can begin before the condition becomes more severe.

Another study is looking at the recovery obstacles faced by survivors of autoimmune encephalitis and their caregivers. Researchers hope that by having a more thorough understanding of what it means to live with the effects of encephalitis, practitioners will be able to develop more effective therapies and support systems.

*The medical information we gather and publish is vetted and intended to be up to date, accurate and express a spectrum of recognized scientific and medical points of view. The information comes from a nucleus of informed scientists, medical doctors, peer-reviewed scientific journals and the National Institute of Health. Please note, differing points of view among scientists and physicians are common. Every effort is employed to ensure the accuracy of these different points of view. That notwithstanding, it is incumbent on persons using this information to consult with his/her physician before reaching any conclusions. Our medical information and publications are not intended to be a substitute for consultation with one’s physician.

Encephalitis Research

Scientists are working on several research projects to expand on what is known about Encephalitis. The research will improve knowledge about the factors that increase the risk for Encephalitis, as well as the causes, and best treatments and cures, and will aid people living with Encephalitis and their caregivers.

We are currently gathering the information required to support projects such as Safety and Immunogenicity Study of the Western Equine Encephalitis (WEE) Vaccine, Efficacy of Ocrelizumab in Autoimmune Encephalitis, and Venezuelan Equine Encephalitis Monovalent Virus-Like Particle Vaccine (VEEV).

*The medical information we gather and publish is vetted and intended to be up to date, accurate and express a spectrum of recognized scientific and medical points of view. The information comes from a nucleus of informed scientists, medical doctors, peer-reviewed scientific journals and the National Institute of Health. Please note, differing points of view among scientists and physicians are common. Every effort is employed to ensure the accuracy of these different points of view. That notwithstanding, it is incumbent on persons using this information to consult with his/her physician before reaching any conclusions. Our medical information and publications are not intended to be a substitute for consultation with one’s physician.

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