Detection and Genetic Analysis of HPAI H5N1 Viruses in Cats during the Fatal Disease Outbreak in Poland: Insights and Recommendations


In June 2023, Poland experienced a fatal disease outbreak affecting cats, which raised concerns about potential zoonotic transmission and the origin of the virus responsible.

This article presents a detailed report on the detection and genetic analysis of the highly pathogenic avian influenza (HPAI) H5N1 virus in ill cats and the potential links to other wildlife and poultry.

The investigation was based on an unofficial cat owner database, which indicated a nationwide distribution of suspected cat cases related to the outbreak.

Genetic Analysis and Phylogenetic Insights

Genetic analysis of the HPAI H5N1 viruses detected in cats revealed that they belonged to clade and exhibited two mutations (E627K and K526R) in the PB2 gene. These mutations are considered mammalian adaptation markers and suggest a potential capacity for cross-species transmission. Interestingly, the cat-derived viral sequences were closely related to an HPAI H5N1 virus sequence obtained from a stork, which also belonged to clade but only carried the K526R mutation.

Transmission Investigation

To investigate the potential routes of transmission, samples of food consumed by ill cats before the onset of symptoms were collected and analyzed. In one case, chicken meat from the same household as an ill cat was found to contain a virus with a high degree of similarity to the cat viruses, bearing both the E627K and K526R mutations.

This finding suggested a possible route of transmission from poultry to cats, but it could not be conclusively confirmed due to limitations in tracing the origin of the chicken meat sample.

The virus isolate from the chicken meat demonstrated its ability to infect both canine and feline cells, raising concerns about zoonotic potential.

Limitations of the Study

The study had several limitations that need to be acknowledged. The origin of the virus found in the chicken meat could not be confirmed, and the possibility of post-butchery, transport, or household contamination should be considered. Additionally, the cat cases were not conclusively identified as HPAI H5N1 infections, and the meat samples analyzed might not have been the only variety of meat consumed by the cats. The reliance on an uncurated community-based cat owner database also introduced uncertainties in data interpretation, although it served as a valuable resource in the early stages of the outbreak.


Based on the presented data, it is crucial to assess the presence of the HPAI H5N1 virus in both wild and farmed settings, as well as locations where potential virus adaptation may occur. Environmental testing may be recommended to investigate non-food-related routes of transmission, and wild birds without apparent pathology should be tested as well. Further epidemiological analysis may reveal potential links between cases and shed more light on the source of infection.


The detection and genetic analysis of HPAI H5N1 viruses in ill cats during the outbreak in Poland highlight the importance of vigilance in monitoring and understanding zoonotic diseases. The study’s findings raise concerns about the potential for cross-species transmission from poultry to cats and possibly to humans.

While there are limitations in the study, community initiatives like the cat owner database play a critical role in providing essential information during early outbreaks. Moving forward, comprehensive surveillance efforts and collaborative research are essential to mitigate the risks of future outbreaks and potential pandemics.

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