Arboviral Encephalitis Fact Sheet
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. Recently, cases of encephalitis due to a West
Nile-like virus have occurred in the New York City area.
These arboviruses, which are usually found in birds or small
rodents, are transmitted to humans by the bite of an infected
mosquito; they are not spread directly from animal to human
or human to human.
Arboviral infections are most common in the summer and
early fall. In Maryland, human cases of arboviral encephalitis
rarely occur; there have been no reported cases in the 1990s.
Most people who are infected with an arbovirus either do
not get sick or have mild symptoms
A small percentage of infected people develop symptoms
of encephalitis; these symptoms may include:
- Fever
- Headache
- Disorientation
- Weakness or Paralysis
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- Seizures
- Coma
- Personality changes
- Other neurological problems
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Symptoms usually occur 5-15 days after exposure to a mosquito
carrying the virus. Young children and the elderly are most
susceptible to severe illness.
There is no specific treatment for arboviral encephalitis
There is no specific medicine available that will kill
the virus. However, supportive treatment can relieve some
symptoms. Most people will recover from the illness, but
permanent neurological problems and death can occur.
Steps you can take to prevent arboviral encephalitis
include:
- Remove standing water (such as water in old tires, buckets,
bird baths, clogged gutters etc.) around the home.
- Wear clothing that covers the arms, legs, and feet in
order to prevent mosquito bites.
- Use mosquito repellents sparingly on exposed skin. An
effective repellent will contain 20% to 30% DEET. Higher
concentrations may cause side effects, particularly in
children. Follow package instructions carefully.
- Spray clothing with insecticides such as DEET or permethrin
to prevent mosquitoes from biting through thin clothing.
- Minimize outdoor activities at dawn, dusk, and in the
evening when mosquitoes are most active.
- Inspect window and door screens and repair any holes found.
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