<abstract xmlns="http://www.w3.org/1999/xhtml">

<sec id="j_jvetres-2022-0017_s_005">
<h3>Introduction</h3>
<p>Highly pathogenic avian influenza (HPAI) outbreaks caused by the Gs/Gd lineage of H5Nx viruses occur in Poland with increased frequency. The article provides an update on the HPAI situation in the 2020/2021 season and studies the possible factors that caused the exceptionally fast spread of the virus.</p></sec>
<sec id="j_jvetres-2022-0017_s_006">
<h3>Material and Methods</h3>
<p>Samples from poultry and wild birds delivered for HPAI diagnosis were tested by real-time RT-PCR and a representative number of detected viruses were submitted for partial or full-genome characterisation. Information yielded by veterinary inspection was used for descriptive analysis of the epidemiological situation.</p></sec>
<sec id="j_jvetres-2022-0017_s_007">
<h3>Results</h3>
<p>The scale of the epidemic in the 2020/2021 season was unprecedented in terms of duration (November 2020–August 2021), number of outbreaks in poultry (n = 357), wild bird events (n = 92) and total number of affected domestic birds (approximately ~14 million). The major drivers of the virus spread were the harsh winter conditions in February 2020 followed by the introduction of the virus to high-density poultry areas in March 2021. All tested viruses belonged to H5 clade 2.3.4.4b with significant intra-clade diversity and in some cases clearly distinguished clusters.</p></sec>
<sec id="j_jvetres-2022-0017_s_008">
<h3>Conclusion</h3>
<p>The HPAI epidemic in 2020/2021 in Poland struck with unprecedented force. The conventional control measures may have limited effectiveness to break the transmission chain in areas with high concentrations of poultry.</p></sec>
</abstract>

Introduction
Highly pathogenic avian influenza (HPAI) outbreaks caused by the Gs/Gd lineage of H5Nx viruses occur in Poland with increased frequency. The article provides an update on the HPAI situation in the 2020/2021 season and studies the possible factors that caused the exceptionally fast spread of the virus.

Material and Methods
Samples from poultry and wild birds delivered for HPAI diagnosis were tested by real-time RT-PCR and a representative number of detected viruses were submitted for partial or full-genome characterisation. Information yielded by veterinary inspection was used for descriptive analysis of the epidemiological situation.

Results
The scale of the epidemic in the 2020/2021 season was unprecedented in terms of duration (November 2020–August 2021), number of outbreaks in poultry (n = 357), wild bird events (n = 92) and total number of affected domestic birds (approximately ~14 million). The major drivers of the virus spread were the harsh winter conditions in February 2020 followed by the introduction of the virus to high-density poultry areas in March 2021. All tested viruses belonged to H5 clade 2.3.4.4b with significant intra-clade diversity and in some cases clearly distinguished clusters.

Conclusion
The HPAI epidemic in 2020/2021 in Poland struck with unprecedented force. The conventional control measures may have limited effectiveness to break the transmission chain in areas with high concentrations of poultry.

Highly pathogenic avian influenza H5Nx in Poland in 2020/2021: a descriptive epidemiological study of a large-scale epidemic

Journal of Veterinary Research

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

Introduction
Highly pathogenic avian influenza (HPAI) outbreaks caused by the Gs/Gd lineage of H5Nx viruses occur in Poland with increased frequency. The...

Highly pathogenic avian influenza H5Nx in Poland in 2020/2021: a descriptive epidemiological study of a large-scale epidemic

Published Online: Mar 25, 2022

Page range: 1 - 7

Received: Nov 12, 2021

Accepted: Mar 10, 2022

DOI: https://doi.org/10.2478/jvetres-2022-0017

Keywords
highly pathogenic avian influenza, H5Nx, poultry, wild birds.

© 2022 K. Śmietanka et al. published by Sciendo

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

Highly pathogenic avian influenza H5Nx in Poland in 2020/2021: a descriptive epidemiological study of a large-scale epidemic

Published Online: Mar 25, 2022

Page range: 1 - 7

Received: Nov 12, 2021

Accepted: Mar 10, 2022

DOI: https://doi.org/10.2478/jvetres-2022-0017

Keywordshighly pathogenic avian influenza, H5Nx, poultry, wild birds.

© 2022 K. Śmietanka et al. published by Sciendo

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

Keywords
highly pathogenic avian influenza, H5Nx, poultry, wild birds.