HomeMy WebLinkAboutMemo - Mail Packet - 06/25/2024 - Memorandum from Matt Parker re 2024 West Nile Virus – Program Orientation and Seasonal Outlook (2)Natural Areas Department
1745 Hoffman Mill Road
PO Box 580, Fort Collins, CO 80522
970-416-2433
mparker@fcgov.com
CC: Kelly DiMartino, City Manager; Mike Calhoon, Parks Director; Katie Donahue, Natural Areas Director
MEMORANDUM
Date: June 17, 2024
To: Mayor and City Councilmembers
Through: Tyler Marr, Deputy City Manager
Dean Klingner, Community Services Director
From: Matt Parker, Natural Areas Ecological Stewardship Manager
Subject: 2024 West Nile Virus – Program Orientation and Seasonal Outlook
BOTTOM LINE
West Nile Virus (WNV) is an annual, seasonal threat to the health of community members.
Trapping data suggests that although WNV is always present, current levels do not present
appreciable risk. Upon the first report of a WNV-positive lab result, staff will provide weekly
memos updating the City Council on the current WNV risk.
BRIEF BACKGROUND ON WEST NILE VIRUS
Only two of the 12 mosquito species that exist in the area transmit WNV. The bird population
then sustains WNV as the reservoir host. Through the summer, the virus amplifies within the
avian community, increasing the likelihood that a mosquito will become infected with WNV and
then bite a human. Although WNV presents higher risk to older individuals and those working
outdoors, WNV infection can be life-altering or fatal to anybody, regardless of age or health.
Over the past 20 years, the City of Fort Collins, in collaboration with the Larimer County
Department of Health and Environment (LCDHE), the U.S. Centers for Disease Control, and
Colorado State University, has developed a comprehensive program to mitigate WNV risk within
the community. This program focuses on disease mitigation and prevention as opposed to other
regional programs that primarily focus on nuisance mosquito abatement. The City and LCDHE
mitigate the risk of WNV through increasing public awareness, reducing mosquito larvae
production, and applying adult mosquito control insecticide when weekly data exceeds the
policy threshold, and such action is recommended by LCDHE.
To reduce mosquito larvae production, Vector Disease Control International (VDCI) conducts
mosquito surveillance that includes mapping mosquito breeding sites throughout the season.
VDCI applies larvicide to breeding sites within an area extending approximately two miles
beyond the City growth management area. The larvicide is a natural, non-toxic biological
product that affects only mosquitoes and some members of the black fly family and is not
harmful to fish and animals.
The City operates a network of 53 traps providing a weekly snapshot of WNV distribution in
most areas of the community. Through this trap network, staff can calculate a vector index to
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determine the WNV risk level. The vector index is a calculation of the abundance of the two
species capable of transmitting WNV and the rate of WNV infection within those mosquitoes.
LCDHE issues a recommendation to spray adult mosquitoes if a 5-trap dataset exceeds the
vector index value of 0.75, as per City resolution.
Certain patterns have emerged after 19 years of data collection, including an early season pulse
of mosquitoes unable to transmit WNV. 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 a subsequent increase in
WNV. Additionally, the northeast and southeast quadrants of Fort Collins routinely show strong
tendencies for higher WNV-risk values.
SEASONAL OUTLOOK FOR JULY-SEPTEMBER 2024
The National Oceanic and Atmospheric Administration climate models predict below average
precipitation for the May through July period and slightly above-normal temperatures extending
into the July-September period. These weather patterns are based on the expected swing from
El Nino conditions toward La Nina. The abundance of mosquitoes and the occurrence of WNV
can loosely be related to the amount of precipitation received throughout the spring and summer
months. However, WNV is highly variable and predicting its prevalence is difficult.
REVIEW OF 2023 SEASON AND TECHNICAL ADVISORY COMMITTEE MEETING
The Fort Collins area received near record precipitation in 2023, registering as the fourth wettest
year in 134 years of record keeping. Mosquito abundance was extremely high and WNV-
positive tests were observed earlier than expected. The heightened WNV activity led to the
LCDHE recommending that the City spray mosquitoes on six different occasions. The City
completed these treatments between July 23, 2023, and August 27, 2023. LCDHE identified
high risk treatment areas using the weekly trap data and aligning with City policy to treat the
smallest effective treatment zones.
Following the 2023 WNV season, the Technical Advisory Committee (TAC) met to discuss
programmatic recommendations and improvements for the 2024 season. This year’s key
recommendation included the pursuit of an expanded trapping network to serve areas of Fort
Collins that currently do not have data on which to make management recommendations. The
TAC also indicated appreciation for redesigned and simplified public maps that are consistent
and easier to read. Staff also extended the time that the “bread crumb” track is displayed on the
online map during applications to allow community members to identify the spray area
throughout the following day.
OUTREACH & SPRAY NOTIFICATIONS
The City provides public outreach throughout the summer encouraging the community to remain
aware and take steps to protect themselves from WNV. This includes regular messaging across
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the City’s various print and digital communication tools, newsletters, social media accounts and
the website. During the peak of the season, we display streetlight banners, bus shelter signage
and paid advertising through local media outlets.
If and when the City sprays for mosquitoes, we notify the community through the City’s website
and social media accounts, story placement in local media, targeted outreach to partners
serving vulnerable populations, and direct text and email notification to community members
who have signed up to receive them via NoCoAlerts/LETA or keyword (text message) opt-in.
In previous years those direct notifications also included a phone call/voicemail option.
Beginning this season, we will cease the phone call portion only and shift the notification
through NoCoAlerts/LETA to be via text message and/or email, depending on the recipient’s
account preferences. Technical and staffing limitations have made the phone call option
increasingly challenging to include in a timely and effective way, and limits the WNV program’s
operational flexibility, for example, if the spray date or location needed to change mid-cycle.
Additionally, since adopting keyword notifications, telephone notices are out of scope for this
type of alert through LETA, which prefers phone notifications only for imminent threats.
Staff plan to communicate this change to the public throughout June and July to ensure
subscribers are aware and can update their account preferences to receive text and email
notifications (many current subscribers already receive these notices via multiple methods). This
will include a City-wide postcard mailing, and one final phone notification in late June or early
July to the people currently subscribed.
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