|  West Nile
Virus
The Centers for Disease Control
(CDC) has provided the information below. For more in-depth information on West
Nile Virus, visit the CDC website at www.cdc.gov/
Q. What is West Nile
encephalitis?
A. "Encephalitis" means an inflammation of the brain and
can be caused by viruses and bacteria, including viruses transmitted by
mosquitoes. West Nile encephalitis is an infection of the brain caused by West
Nile virus, a flavivirus commonly found in Africa, West Asia, and the Middle
East. It is closely related to St. Louis encephalitis virus found in the United
States.
Q. Where did West Nile
virus come from?
A. West Nile virus has been commonly found in humans and
birds and other vertebrates in Africa, Eastern Europe, West Asia, and the Middle
East, but until 1999 had not previously been documented in the Western
Hemisphere. It is not known from where the U.S. virus originated, but it is most
closely related genetically to strains found in the Middle East.
Q. Do the findings
indicate that West Nile virus is established in the Western
Hemisphere?
A. The continued expansion of West Nile virus in the United
States indicates that it is permanently established in the Western
Hemisphere.
Q. Is the disease
seasonal in its occurrence?
A. In the temperate zone of the world (i.e.,
between latitudes 23.5° and 66.5° north and south), West Nile encephalitis cases
occur primarily in the late summer or early fall. In the southern climates where
temperatures are milder, West Nile virus can be transmitted year
round.
Q. How do people get
West Nile encephalitis?
A. People become infected by the bite of a
mosquitoes infected with West Nile virus.
Q. What is the basic
transmission cycle?
A. Mosquitoes become infected when they feed on
infected birds, which may circulate the virus in their blood for a few days.
Infected mosquitoes can then transmit West Nile virus to humans and animals
while biting to take blood. The virus is located in the mosquito's salivary
glands. During blood feeding, the virus may be injected into the animal or
human, where it may multiply, possibly causing illness.
Q. Can you get West Nile
encephalitis from another person?
A. No. West Nile encephalitis is NOT
transmitted from person-to-person. For example, you cannot get West Nile virus
from touching or kissing a person who has the disease, or from a health care
worker who has treated someone with the disease.
For additional
information, visit the CDC website at www.cdc.gov/
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