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West Nile Virus

West Nile virus (WNV) is a potentially serious illness transmitted to humans primarily by mosquitoes. Symptoms of WNV often go unnoticed. In fact, about 80 percent of people infected with WNV show no signs of illness. Up to 20 percent of those who are ill exhibit mild symptoms, such as fever, headache, body aches, nausea, vomiting and sometimes swollen lymph glands or a rash on the chest, stomach and back. These symptoms can last for as little as a few days.

About one in 150 people infected with WNV will become severely ill. Symptoms of illness can include high fever, headache, neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness, vision loss, numbness and paralysis. These symptoms may last for several weeks and cause permanent neurological damage.

Preventing WNV

Although some 150 species of mosquitoes are found in the United States, just one species, Culet pippins, is largely responsible for transmitting WNV. Mosquitoes contract WNV by biting infected birds. Infected mosquitoes can then spread the virus to humans and other animals they bite.

Mosquitoes tend to breed in warm weather near standing water, including flooded areas, stagnant ponds and even flower pots, buckets and barrels. To help eliminate mosquitoes and protect against WNV, the National Safety Council recommends:

  • Empty standing water in old tires, cemetery urns, buckets, plastic covers, toys, or other containers.
  • Empty and change the water in bird baths, fountains, wading pools, rain barrels, and potted plant trays at least once a week.
  • Keep swimming pool water treated and circulating, and rain gutters unclogged.
  • Drain or fill temporary pools.
  • Cover as much skin as possible when in mosquito-heavy areas by wearing long-sleeved shirts, long pants and socks.
  • Avoid use of perfumes and colognes when working outdoors.
  • Use an insect repellent containing DEET or Picaridin on skin not covered by clothing.
  • Spray insect repellent on the outside of your clothing (mosquitoes can bite through thin clothing). Don’t spray insect repellent on skin that is clothed.
  • Be extra vigilant when mosquitoes are most active, from dusk to dawn.
  • Keep window and door screens in good repair.
  • Replace outdoor lights with yellow “bug” lights that deter insect.

If you have questions about mosquitoes and their control, call your local mosquito control district or health department. Some neighborhoods are occasionally sprayed to prevent disease and nuisance caused by large mosquito populations.

More information on WNV is available from the Centers for Disease Control and Prevention.