Here is info from emedicinehealth:
“West Nile Virus Overview
West Nile virus is transmitted to humans by a mosquito bite. The virus can cause encephalitis (inflammation of the brain) or meningitis (inflammation of the lining of the brain and spinal cord).
West Nile virus was discovered in 1937 in the West Nile district of Uganda. New interest was created when West Nile emerged in the United States for the first time in the New York City area in August 1999. There were 62 confirmed human cases and 7 deaths during this outbreak, creating widespread concern.
* Since the initial 1999 New York City outbreak, the cases of West Nile encephalitis have been relatively limited. In 2002, there were a total of 480 reported cases in humans and 24 deaths (as of August 28, 2002).
* The distribution of the virus is spreading across the United States, as determined from surveillance of infected birds by the Centers for Disease Control and Prevention. In a little more than a year, West Nile spread to 11 states along the East Coast. In 2002, the virus spread to Florida, Arkansas, Louisiana, and Texas. Cases are also being seen in the Dakotas, Colorado, Nebraska, and Wyoming.
* Whether West Nile encephalitis will present a serious health risk to the United States in the future is unknown. Using precautions directed at limiting contact by mosquitoes is the best preventive measure at this time.
West Nile Virus Causes
West Nile virus is transmitted to humans by the bite of an infected mosquito. Mosquitoes become infected by biting birds that harbor the virus. The virus is not spread from person to person or from infected birds to humans without a mosquito bite. The virus has now been found in 111 bird species and about a dozen mammals.
* How West Nile virus entered New York is not entirely clear. The most likely explanation is that the virus was introduced by an imported infected bird or by an infected human returning from a country where West Nile virus is common. Before the 1999 New York outbreak, West Nile encephalitis had been identified only in Africa, Asia, the Middle East, and only rarely in Europe.
* Most cases of West Nile occur during the warm weather months. Nonetheless, the mild climate in southern states is expected to sustain the mosquitoes beyond those months.
West Nile Virus Symptoms
Signs and symptoms of the West Nile virus infection range from no symptoms at all to a rapidly fatal brain infection. In areas where the virus is common, people are more likely to show no symptoms of the infection or have only a mild, flulike illness rather than a severe brain infection. Even in an area of outbreak, the likelihood of a person developing illness after infection with West Nile virus is about 1 in every 140-300 people.
* West Nile virus infection typically begins with the abrupt onset of fever, chills, muscle aches, headache, and overall feeling of illness. Headache is particularly common and may be severe. The person may have sensitivity to light with pain behind the eyes.
* Most people fully recover. In others, particularly the elderly, the disease can progress to cause encephalitis or meningitis.
* In the 59 people hospitalized during the initial New York outbreak, signs and symptoms included fever (90%), muscle weakness (54%), headache (46%), altered mental status (44%), rash (22%), stiff neck (19%), joint aches (17%), sensitivity to light (15%), and body aches (14%).
When to Seek Medical Care
West Nile virus is transmitted only by mosquitoes during summer months and generally only appears between the months of May to October.
* People who experience signs or symptoms of serious illness, and have been bitten by a mosquito in the geographic area where West Nile virus is known to appear, should see their doctor immediately.
* Most people with mild symptoms of low-grade fever and muscle aches do not have West Nile virus and will not require specific diagnostic testing.
Anyone who has symptoms of severe illness such as mental status changes, high fever, neck stiffness, sensitivity to light, or confusion should go to the hospital’s emergency department immediately. The West Nile encephalitis that occurred during the initial New York outbreak was especially notable for its severe muscle weakness. This is another important warning symptom.
Exams and Tests
Diagnosing West Nile virus infections is generally done through a combination of observing signs and symptoms along with specialized molecular biologic testing for the virus itself.
* Only people with severe symptoms will require further testing. There is no cure for West Nile and therefore little to gain by widespread testing of people with mild symptoms. In addition, there is only limited laboratory capacity for testing at this time.
* Confirmatory diagnosis of West Nile virus infection is generally done by a DNA test called polymerase chain reaction (PCR) or viral culture of fluid around the spinal cord. A doctor sends both blood samples and spinal fluid samples, obtained by lumbar puncture (also called a spinal tap), to a specialized outside laboratory for these tests.
West Nile Virus Treatment
Self-Care at Home
Home care for people who suspect they may have become infected with West Nile virus is fairly limited. There is no specific treatment.
Mild illness does not require therapy other than medications to reduce fever and pain. Avoid aspirin because it presents a risk for a fatal condition known as Reye syndrome, especially in children.
Medical Treatment
There is no known effective antiviral treatment or vaccine to prevent West Nile virus.
* Milder illnesses do not require treatment.
* In severe cases of West Nile virus, intensive supportive therapy is indicated. This includes hospitalization, IV fluids and nutrition, airway management (some people may need a tube to keep the airway open), ventilatory support (some people may need a machine to help them breathe), prevention of secondary infections, as well as good nursing care.
Next Steps
Follow-up
Anyone who has developed West Nile encephalitis should follow up with a doctor regularly to assure that recovery is taking place in an appropriate manner. The most severely affected people may take as long as 6 months to a year to recover. Some may have permanent nervous system problems.
Prevention
The only way to reduce your risk of contracting West Nile virus is by avoiding contact with mosquitoes during the months of April to October. Mosquitoes are active in the early morning, from dawn until 10 am, and in the later afternoon and early evening. Limit your outdoor activities or protect yourself during those times. Take these precautions:
* If outside during dawn and evening hours, when mosquitoes are most active, wear protective clothing such as long-sleeved shirts, long pants, and socks.
* Consider using an insect repellent containing 10-30% DEET solution. Children should not use a DEET repellent stronger than 10% strength. Other precautions when using DEET include avoiding use on infants or pregnant women, avoiding prolonged or excessive use, storing DEET out of the reach of children, and preventing children from applying it themselves. The manufacturer recommends applying DEET first to your own hands and then spreading it lightly on your children.
* You can spray your clothing with repellents containing permethrin or DEET because mosquitoes may bite through thin clothing. Do not apply repellents containing permethrin directly to exposed skin. If you spray your clothing, there is no need to spray repellent containing DEET on the skin under your clothing. For more details on pesticides and their application, check the National Pesticide Information Center.
* Citronella, which is frequently used in outdoor candles, is a good deterrent against mosquitoes; however, it does not provide long-term protection.
* Limiting mosquito habitats and breeding grounds may also help limit human exposure. Mosquitoes lay their eggs in standing water, so dispose of all tin cans, plastic containers, rubber tires, or any other possible water-holding containers from your property. Drain water from pool covers. Make sure roof gutters drain properly. Clean your gutters regularly.
* Make sure your doors and windows have tightly fitted screens without holes.
* Birds who have died from West Nile virus pose no health risk. The disease is only transmitted by a mosquito bite. Mosquitoes become infected by biting birds that harbor the virus. Report dead birds (especially crows and blue jays) to local health officials so they can be tested and the virus tracked. Use gloves if you touch dead birds.
* Development of a vaccine: Since the virus first appeared in New York, researchers began looking for a vaccine. According to the Proceedings of the National Academy of Sciences, US government scientists have now developed a vaccine that protects mice from the West Nile virus infection. Researchers were expected to begin testing the vaccine in monkeys in March 2002, with testing in humans likely to take place in late 2002.
o The vaccine consists of a combination of genes from a virus called dengue and the West Nile Virus. Both the West Nile virus and dengue viruses are flaviviruses, a group of tick- and mosquito-borne organisms that cause diseases such as yellow fever and St. Louis encephalitis. Researchers from the National Institute of Allergy and Infectious Diseases (NIAID) and Walter Reed Army Institute of Research have shown that although the individual flaviviruses differ from one another, their parts can be intermixed with those of dengue virus to form a hybrid that can be used in a vaccine.
o Because this new vaccine consists of a combination of 2 viruses, it offers 2 benefits. First, the vaccine consists mostly of the dengue virus, which does not target the central nervous system. This means that the vaccine will not infect the brain. Second, because the vaccine has West Nile parts, it will stimulate the body to produce strong antibodies to the virus, offering protection against future exposures.
Outlook
The prognosis of West Nile virus is directly related to the severity of the illness and the age of the person with the infection.
* Those with mild infection recover fully with no permanent disability.
* Death occurs in 12% of people with West Nile encephalitis. The elderly are most at risk for death. Younger people recover much more quickly and are much less likely to show signs and symptoms of severe illness. In the New York outbreak, most cases occurred in people 50 years and older.
Multimedia
Media file 1: The Culex mosquito, common to the Eastern United States, is the primary vector responsible for infecting humans with West Nile virus. Prevention of West Nile virus is primarily directed at reducing the mosquito population from May to October and by taking precautions to limit human exposure during these months of high mosquito activity.
Synonyms and Keywords
West Nile virus, arbovirus, flavivirus, West Nile encephalitis, encephalitis, meningoencephalitis, meningitis, WNV, dengue virus, mosquito-borne virus
Authors and Editors
Author: David A Donson, MD, Staff Physician, Department of Emergency Medicine, New York Methodist Hospital.
Coauthor(s): Mai Kim Lai, MD, Staff Physician, Department of Emergency Medicine, Sparrow Hospital, Michigan State University College of Human Medicine; Steven H Silber, DO, FACEP, Clinical Assistant Professor, Department of Emergency Medicine, Weill Medical College of Cornell University; Vice Chair, Department of Emergency Medicine, New York Methodist Hospital.”