Originally discovered in the West Nile area of Uganda in 1937, West Nile virus is a potentially serious mosquito-borne disease that affects humans, birds and horses.  The virus first appeared in the United States in 1999, and by 2004 had arrived in Clark County.  However, by learning about the virus and following some simple precautions, you can dramatically decrease your chances of becoming infected.

West Nile virus is most often spread by the bite of an infected mosquito. Mosquitoes are West Nile virus carriers that become infected when they feed on infected birds. Infected mosquitoes can then spread the virus to humans when they bite.  West Nile virus is not spread from person to person.

The best way to avoid West Nile virus infection is to prevent mosquito bites:

• Use insect repellents while outdoors.  The most effective repellants contain DEET.  However, repellants containing the chemical picaridin or oil of lemon eucalyptus also provide long-lasting protection against mosquito bites.  Check the packaging for a list of active ingredients and directions on proper use.
  
• Wear pants and long-sleeved shirts when outdoors.
  
• Avoid spending time outside at dusk and dawn (when mosquitoes are active).
  
• Eliminate areas of standing water, including bird baths and improperly maintained swimming pools, which support mosquito breeding.

For people who are bitten by an infected mosquito, most (approximately 80 percent) will not show any symptoms at all.  Of the remaining 20 percent, most will develop a mild illness with symptoms similar to the flu.  This illness, called West Nile fever, lasts for several days to several weeks.  Roughly one in 150 people infected with West Nile virus will develop a severe illness called West Nile encephalitis, with symptoms including high fever, headache, neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness, vision loss, numbness and paralysis. 

The Clark County Health District, Clark County Vector Control and the Nevada State Health Division are conducting surveillance to monitor for West Nile virus.  There are three categories of surveillance currently underway: dead bird testing (crows, ravens and magpies), mosquito testing and sentinel chicken flock testing.  Surveillance helps determine the nature and extent of West Nile activity in our area. 

For additional information on West Nile virus, visit the Clark County Health District website at http://www.cchd.org.  To speak with someone via phone, report an improperly maintained swimming pool or report a large number of mosquitoes, call (702) 759-1220.