In consultation with Boulder County Public Health, the City of Longmont uses a calculation known as the Vector Index (VI) to monitor relative risk of West Nile Virus (WNV) transmission week to week. The Vector Index is a function of both the infection rate and abundance of vector species mosquitoes, in our case Culex tarsalis, the largest carrier of West Nile Virus. A VI of 0.75 is considered elevated risk of transmission. Last week our VI was at 4.3. Our current VI is at 16. This is a record high for Boulder County and represents a high risk of transmission.

 As a result, Vector Disease Control International (VDCI) will spray a second application this week, covering all LM map zones and the enhanced zones. Spraying will begin at sunset on Monday night, July 24, 2023, continuing through the evening or early morning, weather permitting. It is likely they will spray again on Thursday evening, as is routine. Should a change of plan occur, that will be posted at longmontcolorado.gov/westnile.

Zones to be sprayed Monday are: (Find the map of these zones on the VDCI’s webpage.)

• The Shores  (LM-17)
• Garden Acres Park (LM-10)
• Lanyon Park/Stoney Ridge (LM-41)
• Jim Hamm Nature Area (LM-03)
• Union Reservoir (LM-23)
• Rough & Ready South (LM-43)
• Izaak Walton Park (LM-42)
• Great Western Cattail Court (LM-44)
• Sandstone Ranch (LM-22)
• Creekside (LM-31)
• Renaissance (LM-34)
• St Vrain Greenway (LM-28)  
• Enhanced Zones SW-2N & SW-2S
• Enhanced Zone E-1E
• Enhanced Zone E-3

View the boundaries of the predetermined spray areas on the VDCI West Nile Virus webpage and map. When the triggering events occur, notice is typically provided on this webpage on Tuesdays that spraying will occur later that week – typically on Thursday evenings – giving residents 48 hours’ notice of any spraying.

Receive Notifications Related to West Nile Virus

VDCI maintains a database of Longmont residents who have made notification or shutoff requests for their property if spraying is scheduled. Please contact VDCI to request notification, shutoff, or both by filling out the form at the bottom o the www.vdci.net/colorado/ webpage or by calling 877-276-4306.

Additional Prevention

Boulder County Public Health and Longmont officials urge residents to take necessary precautions to protect themselves. Keep safe this summer, and remember the 5Ds:

• Use DEET-enhanced insect repellent or alternative.
• DRESS in light colors and loose fitting long sleeves and pants.
• Avoid the outdoors from DUSK until DAWN.
• DRAIN standing water outside your home.

General Info on West Nile Virus

WNV is transmitted to humans from the bite of an infected female mosquito. 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 death.

Symptoms of WNV include fever, extreme fatigue, headache, body aches, and occasionally can also include skin rashes and swollen lymph nodes. Generally, symptoms appear 3 to 14 days after being bitten by an infected mosquito. Anyone who experiences these symptoms should consult their health care providers. There is no treatment, cure, or human vaccination for the virus. Health care providers can only treat the symptoms to help patients feel better and possibly recover more quickly.

Generally, the mosquito season extends from late April until mid-October, with the end of the season usually signaled by the first hard freeze in the fall.

For more information about West Nile Virus, mosquito activity in Boulder County, or proactive steps to take, call the Colorado Health Information Line at 1-877-462-2911 or  visit Boulder County’s West Nile Virus webpage. To report nuisance mosquitoes, click on “Report Mosquito Activity” in the “What You Can Do” section on the website.

Learn more about West Nile Virus, the City’s integrated pest management program and how to protect yourself from West Nile Virus on the City’s West Nile Virus webpage or by calling 303-651-8416.