Jennifer Peaslee
August 8, 2019

Current WNV Positive Cases 2021 (updated Oct. 28, 2021)

Date Species County
 10/14/21  Red-tailed Hawk  Saratoga
 10/11/21  American Crow  Tompkins
 10/6/21  Merlin  Nassau
 9/20/21  Red-tailed Hawk  Erie
 9/27/21  American Crow  Onondaga
 9/28/21  American Crow  Broome
 9/8/21  Blue Jay  Nassau
 9/14/21  American Crow  Broome
 9/20/21  Fish Crow  Onondaga
 9/17/21  Fish Crow  Oneida
 9/16/21  Double-crested Cormorant  Schoharie
 9/8/21  Fish Crow  Rensselaer
 8/24/21  American Crow  Tompkins
 7/30/21  American Crow  Tompkins
 7/9/21  American Crow  Chemung
 7/9/21  American Crow  Chemung
 7/9/21  American Crow  Chemung

The first positive cases of West Nile Virus for the 2021 season were three American Crows from Chemung county submitted the first week of July, testing returned positive on all three on July 9, 2021.

Current WNV Positive Cases 2020 (updated Feb. 1, 2021)

Date Species County Exception*
1/29/21* American Crow Erie *Submitted 8/10/20, tested 1/29/21
1/29/21* American Crow Erie  *Submitted 9/16/20, tested 1/29/21
11/4/20* Bald Eagle  Genesee Euthanized 9/23, submitted 11/4
10/30/20* Bald Eagle Broome Received 9/1, submitted 10/30
9/14/20 Cooper's Hawk Suffolk  
9/14/20 Red-Tailed Hawk Suffolk  
9/14/20 Yellow-billed Cuckoo  Kings    
9/9/20 Great Horned Owl Onondaga   
8/18/20 Red-Tailed Hawk  Richmond  
8/18/20 Cooper's Hawk Nassau  
8/18/20 Cooper's Hawk Nassau   
8/18/20 Cooper's Hawk Nassau  
7/20/20  American Crow  Suffolk   

The first positive West Nile Virus of the 2020 season was a juvenile American Crow from Suffolk county submitted on July 20. While this first case it a little later than normal based on 2017-2018 results, it is earlier than last year's start, which was early August when we saw our first positive case and that was an American crow as well.

Current WNV Positive Cases 2019 (updated Sept. 12, 2019)

Date Species County
8/5/19   American Crow   Tompkins  
8/15/19 Red-Tailed Hawk Onondaga
8/26/19 Red-Tailed Hawk Erie
8/28/19 Bald Eagle Herkimer
8/28/19 Peregrine Falcon Monroe
9/10/19 American Crow Onondaga

We are well into the 2019 mosquito season and have been holding our breath waiting for the first West Nile Virus case to come through. Almost one month later than our first case seen last year (7/10/2018), we have received our first WNV positive result of 2019. An American crow from Tompkins County was found dazed and close to people and submitted to the Janet L. Swanson Wildlife Health Center for assessment, the bird died the same day. Blood was submitted to CWHL for testing and returned positive WNV results today. Please see listings below for historical results. Raptors and crows are particularly sensitive to West Nile infections, and crows have a high mortality rate. Other species may have mild or no symptoms from infection. 

Current WNV Positive Cases 2018 (updated October 26, 2018)

Date Species County
7/10/2018 Red-Tailed Hawk Steuben
7/13/2018 American Crow Genesee
7/19/2018 Great Horned Owl Tioga
7/21/2018 Red-Tailed Hawk       *Suspect-WNV Tompkins
7/30/2018 American Crow Tompkins
7/31/2018 Red-Tailed Hawk Schenectady
7/31/2018 Cooper's Hawk Albany
7/31/2018 American Crow Albany
8/2/2018 Broad-Winged Hawk    *Suspect-WNV Tioga
8/1/2018 Red-Tailed Hawk Delaware
8/1/2018 American Crow Broome
8/1/2018 American Crow Tompkins
8/1/2018 Great Horned Owl Herkimer
8/2/2018 American Crow Tioga
8/2/2018 Cooper's Hawk Erie
8/3/2018 Fish Crow Schenectady
8/3/2018 American Crow Schenectady
8/6/2018 American Crow Tompkins
8/6/2018 American Crow Tompkins
8/6/2018 American Crow Seneca
8/7/2018 Blue Jay Tompkins
8/8/2018 Cooper's Hawk Erie
8/14/2018 American Crow Rockland
8/14/2018 American Crow Dutchess
8/14/2018 American Crow Colombia
8/13/2018 Red-Tailed Hawk Onondaga
8/13/2018 Red-Tailed Hawk Cortland
8/13/2018 Cooper's Hawk Albany
8/14/2018 Red-Tailed Hawk Washington
8/15/2018 American Crow Albany
8/20/2018 American Crow Albany
8/21/2018 American Crow Broome
8/21/2018 American Crow Cortland
8/21/2018 American Crow Delaware
8/21/2018 Red-Tailed Hawk Chemung
8/22/2018 American Crow Steuben
8/23/2018 American Crow Delaware
8/24/2018 American Crow Chautauqua
8/28/2018 Red-Tailed Hawk Steuben
8/28/2018 American Crow Monroe
8/28/2018 American Crow Genesee
8/28/2018 American Crow Ontario
8/30/2018 American Crow Delaware
8/30/2018 American Crow Delaware
9/4/2018 American Crow Delaware
9/4/2018 American Crow Albany
9/6/2018 American Crow Rensselaer
9/10/2018 Bale Eagle Wayne
9/10/2018 Double-Crested Cormorant Erie
9/10/2018 Double-Crested Cormorant Erie
9/10/2018 American Crow Niagara
9/11/2018 Red-Tailed Hawk       *Suspect-WNV Dutchess
9/11/2018 Broad-Winged Hawk Ulster
9/11/2018 American Crow Warren
9/11/2018 American Crow Albany
9/11/2018 Red-Tailed Hawk       *Suspect-WNV Cortland
9/11/2018 American Crow Tompkins
9/11/2018 American Crow Tompkins
9/12/2018 American Crow Tompkins
9/12/2018 Red-Tailed Hawk Onondaga
9/12/2018 Red-Tailed Hawk        *Suspect-WNV Chemung
9/12/2018 American Crow Orange
9/12/2018 American Crow Orange
9/12/2018 Cooper's Hawk Onondaga
9/13/2018 American Crow Saratoga
9/13/2018 American Crow Saratoga
9/14/2018 Double-Crested Cormorant Schoharie
9/14/2018 Blue Jay Yates
9/17/2018 Great Horned Owl Chemung
9/17/2018 Blue Jay Yates
9/17/2018 American Crow Tompkins
9/18/2018 American Crow Schenectady
9/18/2018 American Crow Schenectady
9/19/2018 American Crow Schoharie
9/19/2018 American Crow Schenectady
9/19/2018 Bald Eagle Steuben
9/19/2018 American Crow Columbia
9/19/2018 House Finch Orange
9/19/2018 House Finch Orange
9/25/2018 American Crow Otsego
9/26/2018 Red-Tailed Hawk Seneca
9/26/2018 American Crow Washington
9/26/2018 Common  Raven Washington
9/26/2018 American Crow Dutchess
10/2/2018 Blue Jay Monroe
10/2/2018 American Crow Wayne
10/4/2018 Double-Crested Cormorant Clinton
10/8/2018 American Crow Tompkins


Original Post-July 17, 2018


This is mosquito season, and along with that comes cases of West Nile Virus. A red-tailed hawk from Steuben County is the first avian case of 2018. This first case is later than last year but about average compared to previous years (see historical info below). The bird was found down and was taken to the Janet L. Swanson Wildlife Health Center for assessment. Blood was submitted to CWHL for testing and returned positive WNV results late last week. The bird is alive and receiving supportive care at the clinic. Raptors and crows are particularly sensitive to West Nile infections, and crows have a high mortality rate. Other species may have mild or no symptoms from infection. 

Historical WNV testing data from the New York State Wildlife Health Program

Year First Case Last Case Total Positive Cases
2020  July 24 September 1 8
2019 April 10 September 27   10
2018  July 10 October 8 88
2017 April 25 November 26 195
2016 July 8 October 4 35
2015 June 11 October 9 38
2014 July 1 September 16 12
2013 June 23 October 24 92
2012 July 6 October 23 104
2011 July 20 October 6 33


New York City has recently reported a human West Nile case and a number of positive mosquito pools. No human cases have been reported from the rest of the state, and mosquito surveillance is up to the individual counties, many of which don't conduct mosquito pool testing. However, West Nile is presumed to be widely active around New York during the summer and fall. 

In 2017, the CWHL reported a marked increase in WNV positive results over previous years. Our data collection is being used to study how and why these year to year fluctuations occur. Environmental factors like winter temperature, rainfall amounts and timing, and the mosquito species that are active all affect the prevalence rates. 

West Nile Virus Transmission cycle. Image courtesy of CDC