Level 2 Fire Restrictions in effect for western areas of Boulder County. No fireworks, fires, open flame, or shooting (see map and flyer).

Many County services are being offered online. Additionally, a variety of resources are available for those impacted by COVID-19.

Mosquito Monitoring
mosquito on a fingertip

Mosquito Monitoring for West Nile Virus

Vector Index Log

The vector index tell us the relative risk of West Nile virus transmission. The vector index is based on the:

  • Total number of Culex Pipien and Culex Tarsalis – the species that carry West Nile virus
  • Number of infected mosquitoes across an area. The vector index is calculated by determining the average number of infected mosquitoes collected per trap in an area.
  • Emergency spraying may be recommended when the vector index is at 0.75 or higher.

Mosquito Monitoring 2019

Zone 1Zone 2Zone 3
Season WeekVector IndexVector IndexVector Index
May 24 - 30 (Week 22)
May 31- June 6 (Week 23)
June 7 - 13 (Week 24)000
June 14 - 20 (Week 25)000
June 21 - 27 (Week 26)000
June 28 - July 4 (Week 27)000
July 5 - 11 (Week 28)000
July 12 - 18 (Week 29)000
July 19 - 25 (Week 30)000
July 26 - August 1 (Week 31)000
August 2 - 8 (Week 32)PendingPendingPending

NOTE: “—” indicates a single pool was submitted for that zone that tested positive, therefore we were unable to calculate an infection rate or vector index for that zone.

Sentinel Map

Sentinel Zones for mosquito testing

West Nile Data

Contact Us

Vector Control Program

Main: 303-441-1564
Submit a question


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