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News Release

Human West Nile (WNV)Virus Cases Escalating Rapidly in Larimer County

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Department: Health & Environment
Release Date: Aug 9, 2013

Contact Information:

Jane Viste


For Immediate Release


A rapid increase this week in reported human cases of West Nile disease reflects the significant rise in WNV-infected mosquitoes during the second and third week of July.  So far in Larimer County, there are 12 WNV human cases reported, including 4 severe (neuroinvasive) cases, 3 from the Fort Collins area and one from the Loveland area. 


Neuroinvasive cases include meningitis, encephalitis, and paralysis. Case reports are expected to continue to rise from infections that have already occurred but have not yet been diagnosed or reported. 


According to Dr. Adrienne LeBailly, Health Department director, “Unfortunately, by the time a West Nile case is reported to us, it is often 3-4 weeks past the time a patient was bitten, and 2-3 weeks past the onset of symptoms.  Human cases are reported too late to trigger the most effective interventions when many infected mosquitoes are present in the community.”


 Histori­cally (2003-2012),  Larimer County has had one of the highest rates of neuroinvasive WNV disease in the nation.


Beginning the last week of July, the Health Department made recommendations to Larimer County municipalities on the Front Range to spray for mosquitoes to reduce the risk of West Nile infection.  Windsor completed city-wide spraying last week, and Loveland, which has previously sprayed targeted areas, will be conducting an all-city spraying early next week. Thus far, Fort Collins has elected not to do any spraying, nor has Berthoud.


Neighborhoods that wish to reduce the level of infected mosquitoes are encouraged to have their HOAs contract with a licensed mosquito control company if they live in areas where municipalities are not spraying. 


LeBailly stressed that communities and individuals should be alert to this situation and do all they can to prevent human illness.  “It’s important to know that West Nile can result in devastating illness, chronic disability and even death in some people. Although the risk of severe disease increases with age, all the serious cases in Larimer County so far have been in patients under 65.”


In addition to community and neighborhood-level mosquito control, individuals should take personal action to prevent mosquito bites.  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.
  • Keep exposed skin covered or use a repellent when outdoors, especially between dusk and dawn or on cloudy days.
  • Drain standing water in your yard or in your garden.
  • Add mosquito-eating minnows to or a mosquito “dunk” to ornamental ponds that feature still 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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