Encephalitis is refers to brain inflammation. It is caused by a virus. Sometimes, encephalitis can result from a bacterial infection, such as bacterial meningitis, or it may be a complication of other infectious diseases like rabies or syphilis. Encephalitis ranges from mild to severe and may result in permanent neurological damage and death. In the United States, the annual incidence of encephalitis is about 1 in 200,000. Children, the elderly persons are most commonly affected.

There are five major types of arboviral encephalitis in the United States :-

1.St. Louis encephalitis (SLE)
2.Eastern equine encephalitis (EEE)
3.Western equine encephalitis (WEE)
4.LaCrosse (LAC) encephalitis
5.West Nile encephalitis (WNE)

Causes

Viruses and bacteria are believed to account for most cases, but a specific germ is positively identified in fewer than half of all cases. The virus gets into the body through insect bites, skin contact, or in food or drink. Mosquitoes or ticks especially in rural areas may carry the viruses. Some common viruses and viral diseases that can cause encephalitis include :-
Chickenpox
Measles
Mumps
Epstein-Barr virus
Cytomegalovirus infection
Human immunodeficiency virus (HIV)
Herpes zoster virus (shingles)
Polio
Rabies
Viruses carried by mosquitoes

Symptoms

Primary symptoms of encephalitis include sudden fever, stiff neck, malaise, sensitivity to light (photosensitivity), and headache. Other early symptoms include the following :-
Abnormal sleep patterns
Behavioral changes
Exhaustion
Nausea
Muscle stiffness
Sore throat
Upper respiratory tract infection (coughing, sneezing, congestion)
A coma (in severe cases)

Treatment

Doctors generally prescribe an antibiotic immediately until a bacterial cause can be ruled out. If herpes virus is suspected, doctors will put the patient on the anti-viral drug acyclovir.
Surgery to control seizures may be performed in later stages of the disease when neurological deficits stabilize. Surgical procedures, such as functional hemispherectomy and hemispherotomy, may reduce the frequency of seizures and also improve behavior and cognitive abilities. In patients who are very sick, supportive treatment, such as mechanical ventilation, is equally important.
Scientists are currently investigating interferon therapy (a type of immune cell therapy) as a treatment for encephalitis caused by the St. Louis and West Nile viruses.
Most people with encephalitis make a full recovery. In a small percentage of cases, swelling of the brain can lead to permanent brain damage and lasting complications.