Encephalitis is an inflammation of the brain tissue. The most common cause is viral infection. In some cases it can be caused by bacteria or fungi. There are two main types of encephalitis: primary and secondary. Primary encephalitis occurs when a virus directly infects the brain and spinal cord. Secondary encephalitis occurs when an infection starts somewhere else in the body and then travels to your brain. Encephalitis is a rare, but serious disease that can be life-threatening. You should call your doctor immediately if you notice any symptoms of encephalitis.
Symptoms
Most people with viral encephalitis have mild flu-like symptoms, such as:
- Headache
- Fever
- Aches in muscles or joints
- Fatigue or weakness
Sometimes the signs and symptoms are more severe, and might include:
- Confusion, agitation or hallucinations
- Seizures
- Muscle weakness
- Problems with speech or hearing
- Loss of consciousness
In infants and young children, signs and symptoms might also include:
- Nausea and vomiting
- Irritability
Causes
Encephalitis can develop as a result of a direct infection to the brain by a virus, bacterium, or fungus, or when the immune system responds to a previous infection; the immune system mistakenly attacks brain tissue (secondary encephalitis, or post-infectious encephalitis).
Primary (infectious) encephalitis can be split into three main categories of viruses:
- Common viruses - including HSV (herpes simplex virus) and EBV (Epstein-Barr virus)
- Childhood viruses - including measles and mumps
- Arboviruses (spread by mosquitoes, ticks, and other insects) - including Japanese encephalitis, West Nile encephalitis, and tick-borne encephalitis
Secondary (post-infectious) encephalitis: can be caused by a complication of a viral infection. Symptoms start to appear days or even weeks after the initial infection. The patient's immune system treats healthy brain cells as foreign organisms and attacks them. It is still not known why the immune system malfunctions in this way.
In more than 50% of encephalitis cases, the exact cause of the illness is not known.Encephalitis is more likely to affect children, older adults, individuals with weakened immune systems, and people who live in areas where mosquitoes and ticks are common.
Treatment
Anti-viral medications can help treat herpes encephalitis. However, they aren’t effective in treating other forms of encephalitis. Instead, treatment often focuses on relieving symptoms. These treatments may include:
- rest
- pain killers
- corticosteroids (to reduce brain inflammation)
- mechanical ventilation (to help with breathing)
- lukewarm sponge baths
- anticonvulsants (to prevent or stop seizures)
- sedatives (for restlessness, aggressiveness, and irritability)
- fluids (sometimes through an IV)
You may need to be hospitalized during treatment, especially with brain swelling and seizures.
Encephalitis isn’t always preventable, but you can lower your risk by getting vaccinated for viruses that can cause encephalitis. Also, make sure your children receive vaccinations for these viruses. In areas where mosquitoes and ticks are common, use repellant, and try wearing long sleeves and pants. This may include wearing appropriate clothing, avoiding mosquito-infested areas, avoiding going outside at specific times during the day when there are large numbers of mosquitoes about, keeping the home mosquito-free, using mosquito repellent, and making sure there is no stagnant water around the house.
