Deadly encephalitis can result from several mosquito-borne viruses.

Encephalitis is inflammation of the brain. It is among the most serious conditions linked to mosquitoes and afflicts over 100 Americans annually. (There is also a tick-borne Powassan virus that has been shown to lead to encephalitis in some instances.)

The diseases of major concern in the U.S. for mosquito-borne encephalitis are:

• Eastern equine encephalitis
• La Crosse encephalitis
• St. Louis encephalitis
• West Nile virus encephalitis
• Western equine encephalitis

All the aforementioned diseases start as a virus which usually resolves itself. The greater danger occurs only if the virus worsens. In this case, the virus can invade the Central Nervous System and cause encephalitis. At that point, the disease can take a deadly course. Even those who survive are often left with permanent neurological damage. Age plays a factor, with the very young and the very old more likely to experience permanent brain damage or death.

Symptoms of vector-borne encephalitis.

• Initial mosquito or tick bite
• Clumsiness
• Confusion
• Fever
• Headache
• Memory loss
• Mood changes
• Muscle weakness
• Seizures
• Stiff neck
• Stupor
• Vomiting

Diagnosis of encephalitis.

The underlying virus may be identified by a blood test or other diagnostic procedure. Diagnosing its development into encephalitis may be accomplished via spinal tap, EEG, or brain imaging.

Treatment of encephalitis.

No currently available medication "cures" encephalitis. Rather, treatment is supportive, dealing with relieving the associated swelling of the brain, loss of automatic breathing functions and other symptoms or complications.

Preventing encephalitis.

Since encephalitis is caused by a variety of infections, there is no single vaccine for it. Nor is there any commercially available vaccine for many of the initiating pathogens. The U.S. CDC recommends taking preventive measures against mosquito and tick bites. Important preventive measures are detailed on our pages about mosquitoes and ticks