HomeMy WebLinkAboutMemo - Read Before Packet - 07/15/2025 - Memorandum from Ryan Vincent re West Nile Virus – Spray NotificationNatural Areas Department
1745 Hoffman Mill Road
PO Box 580, Fort Collins, CO 80522
970-416-2493
rvincent@fcgov.com
CC: Mike Calhoon, Parks Director; Katie Donahue, Natural Areas Director; Matt Parker, Natural Areas Ecological
Stewardship Manager 1
MEMORANDUM
Date: July 15, 2025
To: Mayor and City Councilmembers
Through: Kelly DiMartino, City Manager
Tyler Marr, Deputy City Manager
Dean Klingner, Community Services Director
From: Ryan Vincent, Natural Areas Sr. Supervisor
Subject: West Nile Virus – Spray Notification
BOTTOM LINE
Following a recommendation from the Larimer County Department of Health and Environment
(LCDHE), the City will spray for adult mosquitoes on Thursday, July 17, and Sunday, July
20, in parts of the southeast and southwest quadrants. The vector index (VI) in the treatment
zone is 0.93, which exceeds the City’s policy threshold of 0.75.
• The treatment zone includes eight of this week’s 12 WNV-positive traps.
• Current data shows that the West Nile virus (WNV) infection rate is 11 times higher
than the historical average (based on data from 2003 to 2024) and nearly 4 times
higher than in 2023- a year that required six treatments.
• The citywide vector index is nearly 5x higher than average for this time of year.
WNV ACTIVITY ACROSS THE CITY
Week 28 of 37
Quadrant Previous Week VI Current VI Previous Week
Positive Traps
Current Week
Positive Traps
NW 0.00 0.06 0 1
NE 0.09 0.29 1 4
SE 0.17 0.61 3 5
SW 0.10 0.21 1 2
Citywide 0.11 0.34 5 12
Floating Zone NA 0.93* NA NA
*VI Threshold for spraying in a floating zone is 0.75.
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2
LDCHE RECOMMENDED SPRAY ZONE
• The treatment zone is between Taft Hill Road and Ziegler
Road, from Horsetooth Road to Trilby Road.
• The LCDHE initially recommended spraying a larger area (VI of
.81) between Taft Hill Road and I-25, from Horsetooth Road to
Trilby Road
• The original recommended treatment zone was reduced due to
capacity limitations of the City’s contractor, Vector Disease
Control International (VDCI).
OUTREACH EFFORTS TO INFORM RESIDENTS
• The City will post spray information for the community
on fcgov.com/westnile and on its social media accounts. Community members who
signed up for NOCO Alert will also receive notifications.
• Community members can track the progress of spray vehicles in real time using GPS on
the City’s West Nile Virus website.
WNV ACTIVITY COMPARED TO HISTORICAL AVERAGES
While the abundance of Culex mosquitoes (the carriers of WNV) is below average, the infection
rate is higher than average. The increase in infection rate is elevating the vector index.
NEXT STEPS
• City staff will coordinate with VDCI to implement spraying on Thursday, July 17 and
Sunday, July 20, weather permitting. Spraying will start at Dusk.
Docusign Envelope ID: D444F524-1785-4C59-BFF1-2EAC183C1E6B