HomeMy WebLinkAboutMemo - Mail Packet - 9/5/2023 - Memorandum From Matt Parker Re: West Nile Virus (Wnv) – Week 34 Update 1745 Hoffman Mill Road
PO Box 580, Fort Collins, CO 80522-0580
MEMORANDUM
Date: August 29, 2023
To: Mayor and City Councilmembers
From: Matt Parker, Sr. Supervisor, Natural Areas
Through: Kelly DiMartino, City Manager
Tyler Marr, Deputy City Manager
Dean Klingner, Director, Community Services
Mike Calhoon, Director, Parks
Subject: West Nile virus (WNV) – Week 34 Update
Summary:
Although a high number of traps (18) tested positive this week, mosquito abundance
values have finally become more in-line with historic numbers and is therefore helping
keep vector index values lower. It is important to note however that despite a modest
temporary improvement in the WNV conditions, the highest floating zone this week is still very
close to the 0.75 policy threshold.
Current Vector Index:
Week No: 34 Vector Index
Threshold:
Previous Week Vector
Index:
Current Vector
Index:
FC – Zone NW NA 0.28 0.28
FC – Zone NE NA 0.73 0.29
FC – Zone SE NA 0.08 0.40
FC – Zone SW NA 0.74 0.49
FC – Citywide NA 0.41 0.35
Floating Zone 0.75 1.13 0.73
Current Conditions: This week’s data indicates 18 WNV-positive traps, up from 12 last week.
Both mosquito abundance and infection rates (the two factors producing the vector index) are
within a more historically normal range. With recent rains and the continuance of warm days,
future data points are likely to produce additional spray zones. WNV risk has shifted over the
past two weeks from the Culex tarsalis (associated with regional irrigation) to C. pipiens (the
common house mosquito, associated with small container breeding sites). This transition is not
uncommon and often coincides with elevated risk in the southwest area of the city. Although a
treatment will not occur this week, given the expectation of increased outdoor activity this
holiday weekend, social media posts will remind community members of the ongoing WNV risk.
DocuSign Envelope ID: AEB97E7E-D31F-47FA-BCF2-03CBD81780D6
City of Fort Collins
Process for Spray Recommendations: When the City’s trapping network shows WNV activity
beyond the threshold of 0.75, the Larimer County Department of Health and Environment
(LCDHE) makes a recommendation that the City conduct an application to treat adult
mosquitoes. When an application is recommended, areas of concern are identified based on
data from a minimum of 5 traps. Identified treatment areas may be sub-zone or may cross zone
boundaries.
Outreach and Public Awareness:
WNV-related social media posts will focus on the ongoing risk of WNV, reminding people to
mitigate breeding sites, practice self -protective measures, and sign up for notifications through
LETA.
Throughout the West Nile Virus season, general outreach and education information is centered
on “4Ds” messaging, which encourages people to Drain standing water, Dress in long pants and
sleeves to deter biting, Defend with EPA-approved repellant, and avoid the high mosquito
activity time between Dusk & Dawn. Messaging also encourages community members to opt-in
to receive notification about any future spray events.
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DocuSign Envelope ID: AEB97E7E-D31F-47FA-BCF2-03CBD81780D6