HomeMy WebLinkAboutMemo - Mail Packet - 7/4/2023 - Memorandum From Matt Parker And Mike Calhoon Re: 2023 West Nile Virus – Seasonal Outlook And Program Orientation
Natural Areas Department
1745 Hoffman Mill Road
PO Box 580
Fort Collins, CO 80522
970.416.2815
970.416.2211 - fax
fcgov.com/naturalareas
MEMORANDUM
DATE: June 29, 2023
TO: Mayor and City Councilmembers
FM: Matt Parker, Sr. Supervisor, Natural Areas
Mike Calhoon, Director, Parks
TH: Kelly DiMartino, City Manager
Tyler Marr, Deputy City Manager
Dean Klingner, Director, Community Services
Katie Donahue, Director, Natural Areas
RE: 2023 West Nile Virus – Seasonal Outlook and Program Orientation
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Bottom Line:
The purpose of this memorandum is to provide City Council with an annual update on the status of the
City’s West Nile Virus (WNV) mitigation efforts in advance of the active WNV season. WNV is an annual,
summer-time threat to the health of community members. This memo outlines the City and County
efforts, summarizes the off-season review of the WNV Technical Advisory Committee, and provides a
brief season outlook for 2023.
Brief Background on the City’s WNV Program:
WNV is transmitted by two species of mosquito (as many as 12 species exist in the area), but the virus is
sustained in the region by the bird population. Through the summer weeks, the virus amplifies within
the avian community presenting increased risk to humans. To mitigate this risk, the City of Fort Collins
partners with the Larimer County Department of Health and Environment to increase public awareness,
reduce mosquito larvae production, collect data, and, when necessary, apply adult mosquito control
insecticide.
Nineteen years of data have demonstrated that certain patterns emerge, including an early season pulse
of mosquitoes unable to transmit WNV. This is once again the case with our current mosquito
population showing exceedingly high numbers. As the season progresses, these nuisance mosquito
species will give way to WNV-carrying mosquitoes. The mid-July through mid-September period always
presents increases in WNV-carrying mosquito populations and the subsequent increase in WNV.
Additional patterns include strong tendencies for higher WNV risk values to be associated with the NE
and SE quadrants of Fort Collins.
Last year, the City initiated four adult mosquito insecticide applications in targeted areas. While four
treatments within a year is unusual when looking from an historical perspective, this is in line with the
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intent of the policy to identify the smallest effective treatment zones as early as possible in the
amplification process.
TAC Off-Season Review Summary:
The 2023 WNV off-season TAC meeting focused on a review of the previous WNV season with no
programmatic recommendations for changes for the 2023 season. This is largely the result of the
continued improvement approach for the past 20 years of the program.
Outreach and Awareness:
Public outreach efforts include a focus on increasing the number of community members signed up to
receive Larimer Emergency Telephone Authority (LETA) notices for mosquito spraying. Additional
outreach will continue through the season with outdoor advertising, social media content, and
advertising in key local media outlets.
Seasonal Outlook for WNV July through September:
This year is a year of high production for mosquitoes. As of this weeks’ data, over 90% of the mosquitoes
trapped are Aedes vexans, a floodwater-associated species that does not carry WNV. This is common for
this time of year; however, the abundance of these non-WNV-carrying mosquitoes is at the highest level
since 2017, and generally 2-3x higher than the average level over the past five years.
The National Oceanic and Atmospheric Administration (NOAA) climate prediction models indicate a
pattern slightly leaning toward above-normal temperatures for the next month and extending into the
July-Aug-Sep period, while patterns for precipitation tend to stick near average over the same time
periods. Coupled with higher-than-normal spring precipitation rates we’ve already received and the
associated vegetative growth, this mosquito season could once again be severe.
As the active WNV season begins in late June, staff will provide weekly emails characterizing the current
conditions and data.
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