West Nile Virus Precautions

• Repellents containing DEET have been available since 1956 and are used by an estimated 50 million to 100 million people annually. When used as directed, these repellents have been proven to be safe and effective in preventing mosquito bites.
• The higher the percentage of DEET in a repellent, the longer the protection lasts. Concentrations above 30 percent don't provide better protection.
• Two additional repellents have been registered by the EPA and endorsed by CDC for use: Picaridin and oil of lemon eucalyptus. Picaridin repellents with 7 percent active ingredient provide longer-lasting protection, like DEET, and repellents, with 30 percent oil of lemon eucalyptus as the active ingredient, provide protection equal to a low concentration DEET product.
• If choosing a repellent containing DEET, Coloradoans should select a product containing the right amount of DEET to match the time spent outdoors. Repellents containing 25 percent DEET protect for an average of five hours while repellents containing 20 percent DEET protect for almost four hours; repellents containing 6.65 percent DEET protect for almost two hours; and repellents containing 4.75 percent DEET protect for approximately one-and-a-half hours.
• Use products containing 10 percent to 30 percent DEET or less for children.
• Oil of lemon eucalyptus is not currently recommended for children under 3 years of age, not because it is considered to be dangerous, but because it has not been sufficiently tested on children of that age. Picaridin can be used for children of all ages. Parents and other persons should read container labels thoroughly before applying any mosquito repellents to young children.
• Parents should apply repellent to young children to ensure complete coverage and proper application. Avoid getting the repellent on children's hands or in their eyes or mouths. (Wearing long-sleeved shirts and long pants while outdoors can reduce the need for repellent.)
• Clothing can be sprayed with insecticides containing DEET or Permethrin. This will last up to four washings or two weeks on clothing. It is important to follow product directions.
• Use enough repellent to cover exposed skin or clothing. Don't apply repellent to skin that is under clothing. Heavy application is not necessary to achieve protection.
• Do not apply repellent to cuts, wounds or irritated skin.
• After returning indoors, wash treated skin with soap and water.
• Do not spray aerosol or pump products in enclosed areas.
• Do not apply aerosol or pump products directly to the face. Spray hands and then rub them carefully over the face, avoiding the eyes and mouth.

Other prevention tips include:

• Limit time spent outdoors at dawn or after dusk when mosquitoes that carry West Nile virus are most active.
• If you or members of your family are outdoors, protect yourself by using insect repellent on a regular basis.
• Your back yard or patio is not a "safe zone." Even a brief trip out to the barbecue or garden allows time for an infected mosquito to bite.
• Keep doors and windows closed and/or properly screened to keep mosquitoes out.
• Placing screening on porches also is effective.
• Repair or replace torn or damaged screens.

State and county entomologists have begun trapping and tracking the emergence of Culex tarsalis and other Culex species of mosquitoes, which are the main culprits in transmitting West Nile virus to humans. Mosquitoes become infected with West Nile virus after they bite infected birds that carry it. Mosquitoes then can spread the virus to other birds, humans and horses.

John Pape, a Department of Public Health and Environment epidemiologist who specializes in animal-related diseases and who heads the department's West Nile virus prevention efforts, said that Culex tarsalis mosquitoes are beginning to make an appearance in Colorado again this year. Although none have tested positive for the virus yet, they are expected to soon, he said.

Pape explained, "The disease's 'peak season' will again occur later in the summer when the peak population of these mosquitoes is reached and sufficient numbers of mosquitoes have become infected," which he expects to occur in late-July and through mid-August. "A typically wet spring, followed by a hot summer, can increase the population of infected mosquitoes," he said.

"Weather is one of the biggest factors," Pape said, adding that the incidence of West Nile virus will vary throughout regions of the state. "The warmer temperatures allow the mosquitoes to complete their life cycle faster. We cannot predict yet how severe the West Nile virus season is going to be this year. Our surveillance will start to show that as the season progresses."

A total of 291 human cases of West Nile virus, including four deaths, were reported in Colorado in 2004. This represented a sharp downturn from the first full season of West Nile virus in Colorado in 2003, when there were 2,947 confirmed cases of the disease and 63 deaths.

The Colorado Department of Public Health and Environment and local public health agencies maintain a Web site containing additional information about West Nile virus at www.FightTheBiteColorado.com. Information also can be obtained by calling the toll-free Colorado Help Line, 1-877-462-2911, which is staffed by trained professionals from 7 a.m. to 11 p.m. on weekdays and operates on a reduced schedule on weekends and holidays.