8/7/02

West Nile Virus --- Information , Precautions and Q's & A's

The West Nile Virus (WNV)

In severe cases, the WNV can cause fatal encephalitis, inflammation of the brain.  Less than 1 percent of the people infected with the WNV develop encephalitis, and of those only 3 to 15 percent are fatal.  The incubation period, the time between when the disease in contracted and the time when symptoms appear, ranges from five to fifteen days.  Mild cases usually involve fever, headache, body aches, a mild rash, or swollen lymph glands.  The symptoms of encephalitis are severe headaches, high fever, confusion, muscle weakness and sometimes comas.  In these cases hospitalization, IV fluids and nutrition, airway control, and prevention of other infections (pneumonia, urinary tract) become necessary.

The WNV was first recorded to have infected a woman in Uganda in 1937.  It later appeared in the 1950s in both Egypt and Israel, where it was blamed for several meningoencephalitis deaths among seniors.  The disease is believed to have spread from either infected travelers or imported birds, and was later transmitted by mosquitoes.  Local governments do their part by spraying these areas with pesticides, and continuously testing both birds and insects for the virus.

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What is West Nile Fever?

West Nile Fever (WNF) is a mosquito-borne disease that can cause encephalitis, or inflammation of the brain.  It is caused by the West Nile virus, named after the West Nile district of Uganda where the virus was first isolated in 1937.  The viruses that cause West Nile Fever and St. Louis Encephalitis come from the same family of flaviviruses, and cause diseases that are similar to one another.  West Nile-like virus, like St. Louis Encephalitis, is spread to humans by the bite of infected mosquitoes.  A mosquito becomes infected by biting a bird which carries the virus.  WNF is not spread by person-to-person contact, or directly from birds to persons.

What measures are being taken to protect the population?

Aggressive mosquito control strategy, including mosquito surveillance, testing and aerial and ground spraying activities using Malathion and pyrethroid-based insecticides to reduce the mosquito population and prevent the transmission of mosquito-borne viruses.  Local Departments of Health are working with hospitals and doctors to find and investigate possible causes of encephalitis that may be due to West Nile-like virus.

Where did this West Nile-like virus come from?

West Nile Fever is a disease that has occurred in Egypt, Asia, Israel, South Africa and parts of Europe.  It has never before been found in the Western Hemisphere.  The New York City Department of Health, the New York State Department of Health and the Centers for Disease Control in 1999 investigated how the West Nile-like virus got into New York City.  Possible explanations are that the virus was introduced by an infected bird or by mosquitoes that were brought into this area from a region where West Nile Fever is known to occur.

What are the symptoms of West Nile Fever?

The symptoms of West Nile virus infection are very similar to those of the St. Louis Encephalitis virus.  Most people who are infected have no symptoms or may experience mild illness such as a fever and headache before fully recovering.  In some individuals, particularly the elderly, West Nile Fever can be a serious disease that affects the central nervous system.  At its most serious, it can cause permanent neurological damage and can be fatal.  Symptoms generally occur 5-15 days following the bite of an infected mosquito, and range from a slight fever, headache, rash, swollen nodes and conjunctivitis (irritation of the lining of the eye) to the rapid onset of severe headache, high fever, stiff neck, disorientation and muscle weakness.

Who is at risk of contracting West Nile Fever?

Anyone can become infected with the virus.  However, the elderly are more likely to become ill and develop serious symptoms when infected.

If I live in an area where birds with West Nile Fever have been reported, and I am bitten by a mosquito, am I likely to get sick?

No.  Even in areas where mosquitoes do carry the virus, very few mosquitoes -- perhaps only one out of 1,000 --- are infected.  Your chances of being bitten by an infected mosquito are very small.

But if I am bitten by an infected mosquito, won't I get sick?

Probably not.  Even if you are bitten by an infected mosquito, your chances of developing illness are roughly one in 300.

I have a mosquito bite.  Should I be tested for West Nile-like virus?

No.  Most mosquitoes are not infected with the West Nile-like virus.  Illnesses related to mosquito bites are rare.  However, you should see a doctor immediately if you develop symptoms such as high fever, confusion, muscle weakness, severe headaches or your eyes become sensitive to light.  Patients with mild symptoms are likely to recover completely and do not require any specific medication or laboratory testing.

Is there a treatment for West Nile-like virus?

There is no specific treatment.  However, in cases where hospitalization is required, IV fluids and nutrition, airway control and prevention of other infections (pneumonia, urinary tract) may be necessary.  See a doctor immediately if you develop symptoms such as high fever, confusion, muscle weakness, severe headaches or your eyes become sensitive to light.

Is there a vaccine for West Nile-like virus?

No. A vaccine for West Nile Fever does not exist.

How can I avoid being infected with the West Nile-like virus?

The best way to prevent infection with West Nile-like virus is to avoid getting mosquito bites.  Take the following precautions:

* Use insect repellants with no more than 30% DEET.  Use 15% or less DEET for children.  Do not use DEET on infants.

* If you are outdoors wear protective clothing such as long pants, long-sleeved shirts and socks.

* Empty water from outside objects such as bird baths, old tires and any containers in which water accumulates and where mosquitoes may breed.

* Make sure that door- and window-screens do not have holes.

Where do I call if I need more information on West Nile Fever?

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Last modified: July 13, 2007