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News Release

Increasing West Nile-infected mosquitoes in Fort Collins area

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Department: Health & Environment
Release Date: Aug 1, 2014

Contact Information:

Jane Viste 498-6750 on Monday Aug 4 and later

CONTACT:     Adrienne LeBailly, MD, MPH, before Aug 4;        Jane Viste 498-6750 on Aug 4 and later
                        Health and Environment
DATE:           August 1, 2014          
SUBJECT:   Increasing West Nile-infected mosquitoes in Fort Collins area
Fort Collins, CO -- The Larimer County Department of Health and Environment reports a large increase in mosquitoes infected with West Nile virus trapped in Fort Collins this week. 
Ten out of 24 light traps tested from Fort Collins, and one out of six light traps tested from Loveland, contained mosquitoes confirmed to carry West Nile virus (WNV).  [See Fort Collins maps for each week, which can be found at  Map for current week will not be available online until Aug.2 ] Due to weather conditions this week, only the eastern half of the city had traps placed. Under normal circumstances, each of the city’s 43 light traps and 10 gravid traps are run one evening per week, from Sunday night through Thursday morning. 
 “While certain neighborhoods have been confirmed to have WNV-infected mosquitoes, other areas are likely infected as well, so we need to do all we can to lower our risk of becoming infected,” ” said Dr. Adrienne LeBailly, director of the Health Department.  “The level of Culex mosquitoes that can spread West Nile is running 3 to 4 times higher in this week’s traps than the annual average.
The southeast section of Fort Collins has already reached 3 infected mosquitoes per 1,000 trapped, which is the level where human cases are expected to occur. 
The WNV risk index for southeast Fort Collins—also called the Vector Index—which combines the mosquito infection rate with mosquito abundance, is at 0.57 and already exceeds the level that the Health Department as advised the city to use as the threshold to consider spraying(0.50). The city’s adopted policy has set a threshold of 0.75, or 50% higher than the Health Department has recommended, and also requires at least two human cases to be reported in the same week. Human cases are generally reported to public health departments about 3-4 weeks after an infection has occurred.
The Health Department will be reaching out in Fort Collins to homeowner’s associations to encourage them to spray as the threat increases, since the city’s policy will likely preclude timely spraying in high-risk areas. 
Both individual and community actions can help prevent mosquito-transmitted infections. For individuals, the Health Department recommends the following:
  • Use a mosquito repellent that has been proven to be effective against West Nile Virus-carrying mosquitoes. Ones that contain DEET, Picaridin, Oil of Lemon Eucalyptus (with active ingredient PMD, or p-menthane diol) or IR3535 are good choices.
  • Cover up as much as possible, and use a repellent on exposed skin when out during prime Culex mosquito-biting hours (from dusk to dawn).
  • Drain standing water in your yard or in your garden. Empty bird baths twice a week when the weather is hot.
  • Add mosquito-eating minnows to or a mosquito “dunk” to ornamental ponds that hold standing water.
  • Use netting over baby carriers and strollers
  • Keep window screens repaired.
For more tips on what you can do to prevent West Nile virus, or on repellent use, visit: or call 498-6700.
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Additional information:  See for Fort Collins maps of WNV-infected mosquito trap locations for current week and prior week. (Map for current week will not be available online until Aug.2) Generally each trap is tested weekly, although this week’s inclement weather prevented trapping on the west side of town.

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