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Eastern Equine Encephalitis (EEE) is a rare but serious disease caused by a virus. The virus grows in birds that live in freshwater swamps, and it is usually found only in these birds and in mosquitoes that do not bite people. Sometimes the virus gets picked up by other kinds of mosquitoes that bite horses and people. The risk of getting EEE is highest from late July through September. The virus is spread by adult mosquitoes, which are killed by frost in the fall.

Most WNV infections do not cause any symptoms. Mild WNV infections cause fever, headache and body aches, often with a skin rash and swollen lymph glands. In a small percentage of people infected by the virus, the disease can be serious, even fatal. More severe infections can cause headache, high fever, neck stiffness, stupor, disorientation, coma, tremors, convulsions, paralysis and, sometimes, death. Persons older that 50 years of age have a higher risk of developing severe illness.

There is no treatment for WNV infection. Doctors can treat the symptoms of WNV encephalitis. However, approximately 10% of people who become sick enough from the infection to be hospitalized die from it.

If you develop signs of encephalitis, with fever, muscle weakness, and confusion, you should seek medical care immediately.

Most people infected will either have no symptoms or experience a mild illness with symptoms such as a fever, headache and body aches before a full recovery. However, some individuals may develop more serious symptoms that affect brain tissue. These symptoms include the rapid onset of severe headache, high fever, stiff neck, confusion, muscle weakness, and coma. Death may occur in some instances.

Encephalitis means, simply, inflammation of the brain and is usually a very rare consequence of a viral infection. Encephalitis is different from meningitis which is an inflammation of the layers which cover the brain (the meninges) although this also may be the result of a bacterial or viral infection.

Post Infectious Encephalitis (also called Acute Disseminated Encephalomyelitis or ADEM ) – in which an infection outside the brain triggers the body's immune system to attack the brain.

The viruses responsible are often common viruses. They include measles, chicken pox, influenza, enteroviruses (tummy bugs) and herpes simplex I (the cold sore virus). In most cases the virus involved is not identified.

Diagnosis of encephalitis is made where there is evidence of inflammation. The range of possible symptoms and their rate of development vary widely, and are not just found in encephalitis, so making the diagnosis can be difficult.

Prompt treatment with Acyclovir is important. Acyclovir is an anti-viral agent effective against herpes viruses. Although not always identified, herpes simplex I (the cold sore virus) is the commonest known cause of encephalitis in this country. There is no specific treatment, at present, for any other viruses infecting the brain. Other treatments may include anti-convulsants to control seizures and sedatives to reduce agitation.

There is no specific therapy. In more severe cases, intensive supportive therapy is indicated, i.e. hospitalization, intravenous (IV) fluids and nutrition, airway management, ventilator support if needed, prevention of secondary infections (pneumonia, urinary tract, etc.), and good nursing care.