As per the GOI circular on price capping of Orthopaedic Knee implant by NPPA(National Pharmaceutical Pricing Authority), new prices of knee implants have been implemented effective 16th August 2017. For details on knee implant pricing across our hospitals. CLICK HERE | As per GOI’s circular dated 02nd April 2018 on price-capping of stents by NPPA(National Pharmaceutical Pricing Authority), new prices of coronary stents are revised with effect from 01st April, 2018. For details on stent pricing.CLICK HERE
Request an Appointment

Encephalitis

Encephalitis (en-sef-uh-LIE-tis) is inflammation of the brain. Viral infections are the most common cause of the condition.

Encephalitis can cause flu-like symptoms, such as a fever or severe headache. It can also cause confused thinking, seizures, or problems with senses or movement. However, many cases of encephalitis result in only mild flu-like symptoms or even no symptoms.

Severe cases of encephalitis, while relatively rare, can be life-threatening. Because the course of any single case of encephalitis can be unpredictable, it's important to get a timely diagnosis and treatment.

Symptoms Causes Risk factors Complications Prevention

Most people with viral encephalitis have either no symptoms or mild flu-like symptoms, such as the following:

  • Headache
  • Fever
  • Aches in muscles or joints
  • Fatigue or weakness

More-serious cases require prompt medical care. Additional signs and symptoms of more serious encephalitis may include the following:

  • Confusion, agitation or hallucinations
  • Seizures
  • Loss of sensation or paralysis in certain areas of the face or body
  • Muscle weakness
  • Double vision
  • Perception of foul smells, such as burned meat or rotten eggs
  • Problems with speech or hearing
  • Loss of consciousness

Signs and symptoms in infants and young children may also include:

  • Bulging in the soft spots (fontanels) of the skull in infants
  • Nausea and vomiting
  • Body stiffness
  • Inconsolable crying
  • Poor feeding or not waking for a feeding
  • Irritability

When to see a doctor

Get immediate care if you or someone you know is experiencing any of the symptoms associated with more-severe cases of encephalitis. Severe headache, fever and altered consciousness require urgent care.

Infants and young children with any signs or symptoms of encephalitis should receive urgent care.

The exact cause of encephalitis is often unknown, but the most commonly diagnosed cause is a viral infection. Bacterial infections and noninfectious inflammatory conditions also may cause encephalitis.

An infection may result in one of two conditions affecting the brain:

  • Primary encephalitis occurs when a virus or other infectious agent directly infects the brain. The infection may be concentrated in one area or widespread. A primary infection may be a reactivation of a virus that had been inactive (latent) after a previous illness.
  • Secondary (postinfectious) encephalitis is a faulty immune system reaction in response to an infection elsewhere in the body. Instead of solely attacking the cells causing an infection, the immune system also mistakenly attacks healthy cells in the brain.

    Secondary encephalitis often occurs two to three weeks after the initial infection. Rarely, secondary encephalitis occurs as a complication of a live virus vaccination.

Common viral causes

Common causes of encephalitis include:

  • Herpes simplex virus. There are two types of herpes simplex virus (HSV). Either type can cause encephalitis. HSV type 1 (HSV-1) is usually responsible for cold sores or fever blisters around your mouth, and HSV type 2 (HSV-2) commonly causes genital herpes. Encephalitis caused by HSV-1 is rare, but it has the potential to cause significant brain damage or death.
  • Other herpes viruses. Other herpes viruses that may cause encephalitis include the Epstein-Barr virus, which commonly causes infectious mononucleosis, and the varicella-zoster virus, which commonly causes chickenpox and shingles.
  • Enteroviruses. These viruses include the poliovirus and the coxsackievirus, which usually cause an illness with flu-like symptoms, eye inflammation and abdominal pain.
  • Mosquito-borne viruses. Arboviruses, or arthropod-borne viruses, are transmitted by mosquitoes or other blood-sucking insects. Mosquito-borne viruses can cause infections that include West Nile, La Crosse, St. Louis, western equine and eastern equine encephalitis.

    Mosquitoes transfer the virus from a nonhuman host — such as a bird, chipmunk or horse — to humans. Symptoms of an infection may appear within a few days to a couple of weeks after exposure to an arbovirus.

  • Tick-borne viruses. The Powassan virus is a well-known tick-transmitted virus that causes encephalitis in the U.S. and Canada. Symptoms usually appear about a week after exposure to the virus.
  • Rabies virus. Infection with the rabies virus, which is usually transmitted by a bite from an infected animal, causes a rapid progression to encephalitis once symptoms begin. Rabies is a rare cause of encephalitis in the U.S.
  • Childhood infections. Common childhood infections — such as measles (rubeola), mumps and German measles (rubella) — used to be fairly common causes of secondary encephalitis. These causes are now rare because of the availability of vaccinations for these diseases.

Anyone can develop encephalitis. Factors that may increase the risk of the condition include:

  • Age. Some types of encephalitis are more prevalent or more severe in certain age groups. In general, young children and older adults are at greater risk of most types of viral encephalitis. Encephalitis from the herpes simplex virus tends to be more common in people 20 to 40 years of age.
  • Weakened immune system. People who have HIV/AIDS, take immune-suppressing drugs, or have another condition causing a compromised or weakened immune system are at increased risk of encephalitis.
  • Geographic regions. Mosquito-borne or tick-borne viruses are common in particular geographic regions.
  • Season of the year. Mosquito- and tick-borne diseases tend to be more prevalent in spring, summer and early fall in many areas of the United States. In warmer areas of the U.S., however, mosquitoes and ticks may be present year-round.

The complications resulting from encephalitis depend on several factors, including age, the cause of the infection, the severity of the initial illness and the time from disease onset to treatment.

In most cases, people with relatively mild illness recover within a few weeks with no long-term complications.

Complications of severe illness

Injury to the brain from inflammation can result in a number of problems. The most severe cases can result in coma or death.

Other complications — varying greatly in severity — may persist for months or be permanent:

  • Persistent fatigue
  • Weakness or lack of muscle coordination
  • Personality changes
  • Memory problems
  • Paralysis
  • Hearing or vision defects
  • Speech impairments

The best way to prevent viral encephalitis is to take precautions to avoid exposure to viruses that can cause the disease:

  • Practice good hygiene. Wash hands frequently and thoroughly with soap and water, particularly after using the toilet and before and after meals.
  • Don't share utensils. Don't share tableware and beverages.
  • Teach your children good habits. Teach your children to practice good hygiene and to avoid sharing utensils at home and school.
  • Get vaccinations. Keep your own and your children's vaccinations current. Before traveling, talk to your doctor about recommended vaccinations for different destinations.

Protection against mosquitoes and ticks

To minimize your exposure to mosquitoes and ticks, follow these tips:

  • Dress to protect yourself. Wear long-sleeved shirts and long pants if you're outside between dusk and dawn when mosquitoes are most active and when you're in a wooded area with tall grasses and shrubs where ticks are more common.
  • Apply mosquito repellent. The Environmental Protection Agency (EPA) has registered a number of products containing certain chemicals that repel mosquitoes. The registered chemicals are DEET, IR3535, lemon eucalyptus and picaridin. Products with higher concentrations of the active ingredient provide longer protection.

    Lemon eucalyptus isn't recommended for use on children younger than 3 years old.

    Mosquito repellents can be applied to both the skin and clothes. To apply repellent to your face, spray it on your hands and then wipe it on your face. If you're using both sunscreen and a repellent, apply sunscreen first.

  • Use EPA-recommended insecticide. The EPA also recommends the use of products containing permethrin. These products, which repel and kill tics and mosquitoes, are sprayed on clothing, tents and other outdoor gear. Permethrin shouldn't be applied to the skin.
  • Avoid mosquitoes. Refrain from unnecessary activity in places where mosquitoes are most prevalent. If possible, avoid being outdoors from dusk till dawn, when mosquitoes are most active.
  • Keep mosquitoes out of your home. Repair holes in window and door screens.
  • Get rid of water sources outside your home. Where possible, eliminate standing water in your yard, where mosquitoes can lay their eggs. Common problems include flowerpots or other gardening containers, flat roofs, old tires and clogged gutters.
  • Control mosquitoes in standing water. Fill ornamental pools with mosquito-eating fish. Use mosquito dunks — products that are toxic to mosquito larvae — in birdbaths, ponds and garden water barrels.
  • Look for outdoor signs of viral disease. If you notice sick or dying birds or animals, report your observations to your local health department.

Protection for young children

Insect repellents aren't recommended for use on infants younger than 2 months of age. Instead, cover an infant carrier or stroller with mosquito netting.

Tips for using mosquito repellent with children include the following:

  • Always assist children with the use of mosquito repellent.
  • Spray on clothing and exposed skin.
  • Apply the repellent when outdoors to lessen the risk of inhaling the repellent.
  • Spray repellent on your hands and then apply it to your child's face. Take care around the eyes and ears.
  • Don't use repellent on the hands of young children who may put their hands in their mouths.
  • Wash treated skin with soap and water when you come indoors.
© 1998-2015 Mayo Foundation for Medical Education and Research (MFMER). All rights reserved. Terms of use