Encephalitis is an inflammation of the brain
Encephalitis has many different causes including viruses, bacteria, parasites, and toxins. When encephalitis is caused by a virus transmitted by arthropods such as mosquitoes or ticks, it is known as arboviral (short for arthropod-borne) encephalitis.
In the U.S., arboviral encephalitis is usually caused by viruses transmitted by mosquitoes
There are four main causes of arboviral encephalitis in the U.S. These include eastern equine encephalitis, western equine encephalitis, St. Louis encephalitis, and LaCrosse encephalitis. In 1999, there was an outbreak of West Nile encephalitis in the New York area; West Nile virus is closely related to St. Louis encephalitis virus and is found commonly in Africa, Asia, and the Middle East.
These arboviruses, which are usually found in birds or small rodents, are transmitted to humans by the bite of an infected mosquito carrying the virus; they are not spread directly from human to human. Arboviral infections are most common in the summer and early fall. In Maryland, human cases of arboviral encephalitis rarely occur; there were no reported cases in the 1990’s.
Most people who are infected with an arbovirus either do not get sick or have mild symptoms
For those few people who do develop symptoms, those symptoms usually begin 5 to 15 days after a bite from a mosquito carrying the virus. A small percentage of infected people develop encephalitis or meningitis (inflammation of the tissues that cover the brain and spinal cord); symptoms may include:
Young children and the elderly are most likely to have severe illness. There are no proven treatments for arboviral encephalitis. Most people recover from the illness, but permanent brain problems and death can occur.
Steps you can take to prevent mosquito bites and arboviral encephalitis:
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