Questions and Answers
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. How long has West Nile 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. since the early summer of 1999, possibly
Q. Historically, where has West Nile encephalitis occurred worldwide?
A. See map: CDC Link provided below.
Q. How do people get West Nile encephalitis?
A. By the bite of a mosquito (primarily one of the Culex species) that is infected with
West Nile virus. The disease is an infection of the brain that can be transmitted to humans by
mosquitoes that have bitten infected birds. Most people who become
infected with West Nile virus will either never get sick or develop flu-like symptoms. But
the disease can be deadly for those with weakened immune systems and the elderly.
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. After an incubation period of 10 days to 2 weeks,
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 is 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.
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 any dead animals,
including dead birds. Use gloves or double plastic bags to place the carcass in a garbage
Q. Besides mosquitoes, can you get West Nile virus directly from other insects or
A. Infected mosquitoes are the primary source for West Nile virus and caused the recent
outbreak in the New York City metropolitan area. Ticks infected with West Nile virus have
been found in Asia and Africa. Their role in the transmission and maintenance of the virus
is uncertain. However, there is no information to suggest that ticks played any role in
the New York area outbreak.
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 has 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
Q. What are the symptoms of West Nile encephalitis?
A. Most infections are mild and symptoms include fever, headache, and body aches, often
with skin rash and swollen lymph glands. More severe infection may be marked by headache,
high fever, neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle
weakness, paralysis and, rarely, death.
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. How is West Nile encephalitis treated?
A. There is no specific therapy. In more severe cases, intensive supportive therapy is
indicated, i.e., hospitalization, intravenous (IV) fluids, airway management, respiratory
support (ventilator) if needed, prevention of secondary infections (pneumonia, urinary
tract, etc.), and good nursing care.
Q. Is there a vaccine against West Nile encephalitis?
Q. What does the WNV look like under a microscope?
Click picture to enlarge
Q. Where can I get daily updates of West Nile Activity?