HomeMy WebLinkAboutMemo - Mail Packet - 8/24/2021 - Memorandum From Matt Parker Re: West Nile Virus (Wnv) - Week 32 Update - Post First-Treatment 1745 Hoffman Mill Road
PO Box 580, Fort Collins, CO 80522-0580
MEMORANDUM
Date: August 19, 2021
To: Mayor and City Councilmembers
From: Matt Parker, Sr. Supervisor, Natural Areas
Amy Resseguie, Sr. Specialist, Communications & Public Involvement
Tyler Marr, Deputy Director, Information & Employee Services
Through: Darin Atteberry, City Manager
Kelly DiMartino, Deputy City Manager
Seve Ghose, Director, Community Services
Mike Calhoon, Director, Parks
Zoe Shark, Interim Director, Natural Areas
Subject: West Nile virus (WNV) Week 32 Update Post First-Treatment
Summary:
The adult mosquito treatments on the evenings of Thursday, August 12, and Sunday, August 15
were completed without complication. A subsequent treatment is not currently planned.
However, while mosquito abundance has moderated, the infection rate is alarmingly high,
particularly in the northwest area of the city. There is a considerable chance that future data
may lead the Larimer County Health Department to recommend additional treatment.
Current Vector Index:
Week No: 32 Vector Index
Threshold:
Previous Week Vector
Index:
Current Vector
Index:
FC Zone
NW NA 0.00 0.52
FC Zone NE NA 0.21 0.44
FC Zone SE NA 0.62 0.54
FC Zone SW NA 0.14 0.15
FC Citywide NA 0.32 0.44
Floating Zone 0.75 0.76 0.63
Current Conditions: A total of 17 traps tested positive in this week s data. However, it is
important to remember that traps were collected prior to the Thursday evening treatment. Due to
the Thursday/Sunday treatment, data from the treatment area is not considered in the
determination of potential spray zones this week. The data is, however, reflected in the values
above. The highest vector index floating zone is in the north-central area of the city, with a
vector index value of 0.63.
City of Fort Collins
Anticipated Future Conditions: Weeks 30-36 are the historic peak weeks of WNV activity in
terms of both abundance (week 30) and infection rate (week 35).
light on the efficacy of the recent treatment. Both abundance and infection rate are likely to
decrease in the treatment area; however, the infection rate across the city is currently higher
than historic values and is rising. Looking forward to the final month of the WNV season, the
high infection rate in the zones beyond the SE is extremely concerning.
Low overnight temperatures will be the key driver in the seasonal reduction of mosquito
breeding and therefore WNV risk. Extended periods with overnight lows in the 48-51° range will
These
overnight lows are not expected in the next two weeks.
Outreach and Public Awareness:
Staff is updating the WNV webpage weekly with current vector index data, maps of current
WNV positive traps, and a description of the highest risk WNV floating zone. Staff is exploring
the timing and extent of possibly distributing door hangers in the north-central area of the city.
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.
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