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For Immediate Release  • July 17, 2013
Staff Contact: Boulder County Public Health, 303-441-1564

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Boulder County


UPDATE ON 7/17/13 at 3 pm:


Citywide Spraying for Mosquitoes Begins Thursday Friday


July 17, 2013 - The City of Longmont in conjunction with Colorado mosquito Control will begin citywide spraying on Thursday Friday night, July 19 at 9 pm to help control mosquitoes that might be carrying West Nile Virus, weather permitting.

After receiving results from mosquito pool trapping in Longmont, officials from Boulder County Public Health (BCPH), the City of Longmont, and the Colorado Department of Public Health and Environment met to discuss implementation of emergency spraying for the city. To date, there have been 22 mosquito pools that have tested positive for West Nile Virus (WNV) in Boulder County.  There have been 92 pools that have tested positive statewide. There has been one confirmed human case of WNV in Delta County.

In addition to Longmont's plans to spray on Thursday, health officials are also implementing spraying of a one-mile buffer surrounding the city. In addition, BCPH is working closely with Weld County health officials to ensure other areas surrounding Longmont are sprayed.  Additional spraying is also being planned for next Monday, July 22, weather permitting. pending surveillance data collected on Sunday.

The product being used for spraying is Aqualuer. The spray effort is done using an ultra-low volume mist that is intended to impact mosquitoes. Residents can shut windows to prevent spray from drifting into their homes, but the spray levels are set to be toxic to mosquitoes and not to humans.

The Vector Index, a calculation that helps indicate the risk of human WNV infection, from July 9 mosquito pool testing in Longmont yielded an index of 1.32. The index from the July 16 trapping was 1.18. When an index threshold of 0.75 is reached in a given area, county health officials recommend that leaders in affected municipalities implement emergency spraying.

“Mosquito activity so far this year indicates that there is heightened risk for transmission of West Nile virus,” said Jeffery Zayach, BCPH director. “We are fortunate that we had numerous planning discussions with city leaders well in advance of the WNV season and, like surrounding counties, are prepared to make formal recommendations for a spray option in order to protect our residents.”

WNV is a disease that can be transmitted to humans by mosquitoes. While most infections are mild, the more serious infections can cause encephalitis (inflammation of the brain) and/or meningitis (inflammation of the brain's lining), loss of vision, paralysis, coma, tremors, convulsions and in some cases, death.

“Based on data since WNV arrived in Colorado, we have learned that there is a four to six week window period in which spraying is most effective to reduce the human risk of infection,” said Lane Drager, BCPH Consumer Protection program coordinator.

While the recommendation for spraying is only being made for the City of Longmont at this time, public health officials warn that the risk of WNV infection is still very concerning in other parts of the county, “We have found the virus in all areas of Boulder County east of the foothills.  Even if you do not live in Longmont, the risk of infection is increasing, and all county residents should be taking personal precautions. We believe emergency spraying efforts will help prevent illnesses,” said Drager.

Symptoms of WNV include fever, headache, body aches and can occasionally include skin rashes and swollen lymph nodes. Generally, symptoms appear 3 to 14 days after being bitten by a mosquito. Persons who experience these symptoms should consult with their doctor or local community health clinic.

There is no treatment, cure, or vaccination for WNV; health care providers can only treat the symptoms to help patients feel better and possibly recover more quickly. The only treatment available is prevention.

Public health officials remind residents that, as we enjoy these warm temperatures with outdoor activities, particularly at dusk and dawn, it is important that everyone take action to protect themselves by following ALL of the four Ds. The 4 D’s are:


For more information about WNV, please visit the BCPH website at .  To ask specific questions, call the Colorado Health Education Line for the public at 1-877-462-2911 (available in Spanish and English).

If people suspect they have WNV symptoms, BCPH urges them to consult with their primary care physicians.

See additional tips at