After the positive identification of West Nile Virus (WNV) in Longmont mosquito traps and the high numbers of Culex mosquitoes found in the traps, Vector Disease Control International (VDCI) will continue mosquito spraying coverage to all LM map zones and to the enhanced zones in order to control the spread of West Nile Virus.

Spraying is triggered when West Nile Virus-positive mosquitoes are discovered in Larimer, Boulder or Weld Counties and when Longmont traps exceed 150 mosquitoes per trap. In consultation with Boulder County Public Health, we use a calculation known as the Vector Index (VI) to monitor relative risk of 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 and our current VI is at 4.35.

Because of our wet spring weather and subsequent heat, higher than usual numbers of mosquitos are predicted across the region all season long. In keeping with Longmont’s West Nile Virus control plan, the City’s mosquito control contractor, VDCI, will spray to eradicate mosquitoes between 9-11 pm Thursday night, July 20, 2023, weather permitting.

Zones to be sprayed this week 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 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 make a notification or shutoff request by filling out the form at the bottom o the www.vdci.net/colorado/ webpage or by calling 877-276-4306.

There are three ways to receive notifications and/or opt out of spraying near your home:

1. Call Notification Only: VDCI will phone you before spraying in your neighborhood
2. Address Shutoff Only: VDCI will shutoff the spray machine while driving past your property
3. Notification & Shutoff: VDCI will phone you before spraying in your neighborhood and shutoff the spray machine while driving past your property

The City also offers an eNotification system that provides residents with up-to-date information on a variety of topics including West Nile Virus. Visit the eNotification subscription page to sign-up and choose the West Nile category to receive notification when local spraying alerts are issued.

Managing Mosquitoes and Preventing the Spread of West Nile Virus

The City of Longmont works with VDCI to implement an integrated pest management program to combat mosquitoes that might carry the West Nile Virus. Check out the pest management program on our Weed and Pest Management page. This program focuses on attacking mosquitoes before they hatch and become airborne and helps minimize the fogging designed to kill adult, airborne bugs. However, some localized spraying becomes necessary when the West Nile mosquito population increases due to habitat and weather conditions.

VDCI uses state-of-the-art technology, calibrated application timing, and the least toxic products to minimize non-target impacts. All adult mosquito control is accomplished using Ultra Low Volume (ULV) fogging equipment and is performed after dusk when the majority of mosquito species are most active.

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

1. Use DEET-enhanced insect repellent or alternative.
2. DRESS in light colors and loose fitting long sleeves and pants,
3. Avoid the outdoors from DUSK until DAWN.
4. 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.