West Nile virus, which had been active in Africa, Asia, and parts of Europe for decades, first appeared in New York City in 1999.
Since then, the virus has spread across the United States and has accounted for 16,600 cases and 654 deaths according to the Centers for Disease Control and Prevention (CDC). The mosquito-borne illness is now considered a more serious health threat than previously believed.
For several years, West Nile was only regarded as a severe problem for the elderly and infirm and little more than a passing nuisance for the rest of the population. Today, however, West Nile has emerged as a serious threat to young, healthy people in their 30s, 40s, and 50s. Mild cases of the virus may impair people for weeks or months while more severe cases, though still rare, can cause varying degrees of paralysis and even respiratory failure. Dr. Henry Masur of the National Institutes of Health points out that even though West Nile is "fading" somewhat from public consciousness, there are still "more cases of paralysis (from West Nile) than there were in many years of polio."
The strain of West Nile in the United States is a more serious one than that found in much of the world where the virus has relatively mild symptoms and, as result, there is a higher percentage of cases with neurological complications similar to meningitis, encephalitis, and polio. This fact was not apparent to health officials early on. In fact, experts believe that some of the more severe symptoms are mistaken for a stroke or some other paralyzing illness.
Since there is no vaccine for West Nile, the best advice is to avoid contact with mosquitoes by using repellants, stay away from places which are likely mosquito habitats or breeding areas (like tall grass or damp, marshy areas), and not permit water to collect and stand in spots where mosquitoes can breed. If you experience a high fever, severe headache, confusion or difficulty thinking, severe muscle weakness, tremors, or a stiff neck, visit an emergency room or see a doctor immediately.