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 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 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 was made to "West Nile-like" virus. Does this mean the virus found in New York is not West Nile virus? A. Initially, the virus found in New York was identified as being genetically related to West Nile virus. Complete genetic sequencing of virus found in the New York area has now been completed and the virus has been definitively identified as West Nile virus.
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. Is there a vaccine against West Nile encephalitis?
Q. What can I do to reduce my risk of becoming infected with West Nile virus?
* Stay indoors at dawn, dusk, and in the early evening.
* Wear long-sleeved shirts and long pants whenever you are outdoors.
* Apply insect repellent sparingly to exposed skin. An effective repellent will contain 20% to 30% DEET (N,N-diethyl-meta-toluamide). DEET in high concentrations (greater than 30%) may cause side effects, particularly in children; avoid products containing more than 30% DEET.
* Repellents may irritate the eyes and mouth, so avoid applying repellent to the hands of children. Insect repellants should not be applied to very young children (< 3 years old).
* Spray clothing with repellents containing permethrin or DEET, as mosquitoes may bite through thin clothing.
* Whenever you use an insecticide or insect repellent, be sure to read and follow the manufacturer^s DIRECTIONS FOR USE, as printed on the product.
* Note: Vitamin B and "ultrasonic" devices are NOT effective in preventing mosquito bites.
Division of Vector-Borne Infectious Diseases, National Center for Infectious Diseases, Centers for Disease Control and Prevention, Revised October 29, 1999.
(To comment on this topic in the Earth Forum message area, read the West Nile Virus in Birds discussion.)