For more information regarding the on-going investigation
into West Nile-like virus in the New York area, please see the press release,
West
Nile-like virus in the United States.
Q. What is West Nile encephalitis?
A. "Encephalitis" means an inflammation of the brain and can
be caused by viral and bacterial infections, 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. How do people get West Nile encephalitis?
A. By the bite of a mosquito (primarily the Culex species)
that is infected with West Nile virus.
Q. What is the basic transmission cycle?
A. Mosquitoes become infected by feeding on birds infected with
the West Nile virus. Infected mosquitoes then transmit the West Nile virus
to humans and animals when taking a bloodmeal.
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 the virus that causes West Nile encephalitis
from touching or kissing a person who has the disease, or from a health
care worker who has treated someone with the disease.
Q. Can you get West Nile virus directly from birds?
A. There is no evidence that a person can get the virus from
handling live or dead infected birds. However, avoid bare-handed contact
when handling dead animals, including dead birds. Use gloves or double
plastic bags to place the carcass in a garbage can.
Q. Besides mosquitoes, can you get West Nile virus directly
from other insects or ticks?
A. Infected mosquitoes are the primary vector for West Nile
virus and the source of this outbreak. Ticks have been found infected with
West Nile virus in Asia and Africa. Their role in the transmission and
maintenance of the virus is uncertain. However, as it relates to the New
York area outbreak, ticks have not been implicated as vectors of West Nile-like
virus.
Q. What are the symptoms of West Nile encephalitis?
A. Mild infections are common and include fever, headache, and
body aches, often with skin rash and swollen lymph glands. More severe
infection is marked by headache, high fever, neck stiffness, stupor, disorientation,
coma, tremors, occasional convulsions, paralysis and, rarely, death.
Q. What is the incubation period of West Nile encephalitis?
A. Usually 5 to 15 days.
Q. Where did the West Nile-like 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 has not previously been documented in the Western Hemisphere.
It is not known where the U.S. virus came from.
Q. How long has the West Nile-like virus been in the U.S.?
A. It is not known how long it has been in the U.S., but CDC
scientists believe the virus has probably been in the eastern U.S. for
several months, possibly longer.
Q. Reference is made to "West Nile-like" virus. Does this mean the
virus found in New York is not West Nile virus?
A. No, it means that the virus found in New York is genetically
related to West Nile virus, but because of genetic differences it may be
a new subtype of West Nile virus. Laboratory testing to confirm this continues.
Q. When will the current risk of infection end?
A. The risk in the New York City area is greatly reduced due
to the effectiveness of mosquito control and public education programs.
However, the risk of infection will not be completely over until mosquito
activity ceases for the season, i.e., when freezing temperatures are experienced.
Q. What precautions need to be taken to prevent a recurrent outbreak
next year?
A. Surveillance for infected mosquitoes and sentinel bird flocks
for West Nile virus will greatly enhance state and local government's early
detection symptoms.
Q. What is the mortality rate of West Nile encephalitis?
A. Case-fatality rates range from 3% to 15% (higher in elderly
than in younger age groups).
Q. How many cases of West Nile encephalitis occur in the U.S.?
A. No cases have previously been reported in the U.S. prior
to September 1999 (New York). No reliable estimates are available for the
number of cases of West Nile encephalitis that occur internationally.
Q. Do birds naturally infected with West Nile virus die or
become ill?
A. This has not been previously reported, but apparently has
occurred in the New York area epidemic.
Q. How is West Nile encephalitis treated?
A. There is no specific therapy. Intensive supportive therapy
is indicated in more severe cases.
Q. Is the disease seasonal in its occurrence?
A. In temperate areas of the world, West Nile encephalitis cases
occur primarily in the late summer or early fall. In the southern climates
where temperatures are milder, West Nile encephalitis can occur year round.
Q. Who is at risk for getting West Nile encephalitis?
A. All residents of areas where active cases have been identified
are at risk of getting West Nile encephalitis, but persons > 50 years of
age have the highest risk.
Q. Is a woman's pregnancy at risk if she gets West Nile encephalitis?
A. There is no documented evidence that a pregnancy is at risk
due to infection with West Nile virus.
Q. Historically, where has West Nile encephalitis occurred
worldwide?
A. See map:
Q. Is there a vaccine against West Nile encephalitis?
A. No.
Q. What can I do to reduce my risk of becoming infected with West
Nile virus?
A.
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