HomeMy WebLinkAboutMemo - Mail Packet - 9/26/2023 - Memorandum From Matt Parker And Amy Resseguie Re: West Nile Virus (Wnv) - Final Data Week; No Recommendation To Spray 1745 Hoffman Mill Road
PO Box 580, Fort Collins, CO 80522-0580
MEMORANDUM
Date: September 20, 2023
To: Mayor and City Councilmembers
From: Matt Parker, Sr. Supervisor, Natural Areas
Amy Resseguie, Lead Specialist, Communications & Public Involvement
Through: Kelly DiMartino, City Manager
Tyler Marr, Deputy City Manager
Dean Klingner, Director, Community Services
Mike Calhoon, Director, Parks
Katie Donahue, Director, Natural Areas
Subject: West Nile virus (WNV) – Final Data Week; No Recommendation to Spray
Summary:
Recent cooler overnight low temperatures have resulted in an expected seasonal decline in
mosquito activity and abundance, and therefore vector index value. This is the final data point
for the 2023 WNV season. With near record precipitation driving mosquito populations
throughout the region, the 2023 season produced the highest number of testing pools, and the
most significant WNV activity in recent years.
Current Vector Index:
Week No: 37 Vector Index
Threshold:
Previous Week Vector
Index:
Current Vector
Index:
FC – Zone NW NA 0.15 0.00
FC – Zone NE NA 0.00 0.18
FC – Zone SE NA 0.07 0.00
FC – Zone SW NA 0.09 0.00
FC – Citywide NA 0.08 0.00
Floating Zone 0.75 0.25 N/A
Current Conditions: This week’s data shows two WNV-positive traps; down from three last
week. Both positive traps are in the northeast quadrant of Fort Collins. Both abundance and
infection rates match or nearly match historically normal levels for this time of year. As is always
the case, some mosquitoes safely harbor through the winter, which may impact early season
numbers next year. This impact may be greater next year due to the relatively high mosquito
numbers this year.
DocuSign Envelope ID: 32942C18-04CF-4C41-8160-10CB757BF6BE
City of Fort Collins
Season Summary: Near record precipitation levels drove mosquito populations, and therefore
WNV risk, to levels not seen since Northern Colorado’s earliest years of WNV. The entire region
experienced this significant increase. The Larimer County Department of Health and
Environment recommended six adult mosquito treatments in targeted areas of Fort Collins
where the data showed a vector index exceeding 0.75, which is the City’s treatment threshold.
In line with the policy and operational intent to reduce WNV amplification through targeted
treatments, mosquito abundance decreased post application in each of the six treatments.
Reports of human WNV cases typically lag infection dates by two to three weeks, therefore case
data continues to stream into the reporting mechanism. To date, case numbers for 2023
generally show a 4x increase over the 5-year average. Currently, the statewide data shows 18
deaths and 191 neuro-invasive cases. Within Larimer County, 38 total cases have been
reported with 19 cases requiring hospitalization, and two deaths. The case data may continue to
increase with additional reports.
Next Steps:
City and County staff will collaborate to identify opportunities for improvement for the 2024
season. The WNV Technical Advisory Committee will also review the 2023 season and identify
any potential paths of inquiry or operational improvements. The WNV Technical Advisory
meeting will occur in February and additional meetings will be scheduled if significant potential
improvements warrant additional meeting time.
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