CDC light traps, like the one pictured here, are used in Garfield County to monitor mosquito counts and test for West Nile virus.

Take precautions during West Nile season

Centers for Disease Control reports West Nile virus cases are up this year

August 3, 2012

Garfield County, CO – Late summer presents an increased incidence of mosquitoes in Garfield County, creating an increased risk of West Nile Virus. The strongest concentrations of the type of mosquitoes that may carry the virus have been found in the Grand Valley area of Garfield County in recent weeks. This is because that region is warmer and at a lower altitude than the rest of the county, and Mesa and Delta counties have experienced an increase in West Nile occurrences in mosquitoes.

West Nile Virus is carried by certain infected birds and transmitted to people by bites from mosquitoes that have fed on these birds.

“In areas where these mosquitoes are found, less than 1% may be infected with West Nile Virus,” said Dr. Michael Weissmann, a PhD entomologist, and surveillance manager for Colorado Mosquito Control. “Late summer is typically when the risk of West Nile increases, due to higher temperatures.”

Mosquitoes are trapped locally, and a sampling is tested by the Colorado Department of Public Health and Environment (CDPHE) to determine whether West Nile is present. “None of the mosquitoes trapped in Garfield County have tested positive for West Nile this season,” said Steve Anthony, vegetation manager for Garfield County. “Monitoring will continue of the counts using traps set by Colorado Mosquito Control around the county. An update of the prior week’s mosquito monitoring will appear on the county website throughout the summer and early fall every Monday.” Click on, and mosquito count information locally, and resources for West Nile Virus are linked from the home page.

Several more weeks of warm weather lie ahead, presenting a continued risk of mosquito activity. “With this in mind, it is important to remember to take necessary precautions to prevent insect bites,” says Mary Meisner, R.N., and Public Health director. Good prevention includes following the recommendations of the “Fight the Bite!” campaign, and recommendations from the Centers for Disease Control and Prevention (CDC), available online at

Garfield County and statewide health departments also recommend following 4 Ds:

  1. Drain standing water
  2. At dusk and dawn limit outdoor activity, when mosquitoes are most active
  3. Use DEET in insect repellents, utilizing manufacturer recommendations, and
  4. Dress in long sleeves and pants during dusk and dawn

According to the CDC, most people infected with West Nile Virus (about 4 out of 5) will not experience any symptoms. Approximately 20% of people who become infected will develop West Nile Fever. Symptoms typically begin 2-15 days after being bitten by an infected mosquito. These symptoms include fever, headache, tiredness, and body aches, occasionally with a skin rash and swollen lymph glands. The illness can last anywhere from a few days to several weeks. A smaller number of people (about 1 in 150) infected with the virus will develop a more severe form of the disease including headache, high fever, neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness, and paralysis.

Residents can help by reporting standing water or high mosquito activity to Colorado Mosquito Control at or via phone at 1-877-276-4306.