West Nile Virus

WNV Positive Cases (updated Jan. 16, 2025)

We had the year's first positive case of WNV in a NY wild bird last week. On July 12th, a juvenile crow was submitted to the Janet L. Swanson Wildlife Hospital after it was found down and unable to fly by a member of the public in Tompkins County that morning. On examination, the crow was quiet to depressed, and emaciated with neurologic symptoms (ataxia, suspect tremors/seizure-like activity). There was no obvious trauma. An oropharyngeal swab for West Nile Virus testing was submitted and came back positive. 

WNV Positive Cases 2023 (updated Dec. 6, 2023)
We've had our first positive West Nile Virus case this summer season.

WNV Positive Cases 2022 (updated Mar. 13, 2023)
Wild birds are still under fire from the potential for a double threat with HPAI and WNV cycling through avian populations. Please continue to report neurologic birds or groups of multiple bird mortalities to your local DEC wildlife offices.

While we continue to be on the lookout for HPAI, our surveillance of other diseases doesn't stop. We track West Nile Virus (WNV) in wild birds every year. We have received our first WNV positive result for 2022. A Cooper's hawk from Monroe County was found deceased and submitted to the DEC for diagnostic examination; samples and swabs were taken during the necropsy and submitted for testing to determine the cause of death. Crows and raptors, like Cooper's hawks, are particularly sensitive to West Nile infections, and crows have a high mortality rate. Other species may have mild or no symptoms of infection. 

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

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

WNV Positive Cases 2019 (updated Sept. 12, 2019)
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 the 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 of infection.

WNV Positive Cases 2018 - (updated October 26, 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 of infection.

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.

Contact us for additional details regarding our data.