In June 2023, the Poland public health officials notified the World Health Organization of unusual deaths in cats across the country. Dozens were found to be positive for influenza A (H5N1). Fourteen cats are reported to have been euthanized, and a further 11 died, with the last death reported on 30 June. The source of the exposure of cats to the virus is currently unknown and epizootic investigations are ongoing.
Sporadic infection of cats with A(H5N1) has previously been reported, but this is the first report of a high numbers of infected cats over a wide geographical area within a country.
Feline A/H5N1 infections raise concerns that adaptation of avian viruses to cats—animals living in close contact with humans, and hunting birds—could represent the first step towards potential human-to-human transmission of Highly pathogenic avian influenza viruses (HPAIVs).
Nearly all mammalian strains belonging to clade 126.96.36.199b were isolated within last two to three years, even though HPAI outbreaks have been occurring worldwide for over 20 years. The most plausible explanation for this situation is that the clade 188.8.131.52b, with point mutations, is indicative of adaptations to mammalian hosts.
This case report provides the clinical description, along with pathological, virological, and bacteriological results of feline influenza A/H5N1 case, one of the series observed this summer in Poland. The virus was characterized as belonging to the clade 184.108.40.206.b with mutations indicating a mammalian spread.
The source of the infection for the investigated cat remains unknown. The most common routes for cats to contract avian influenza virus appear to be direct contact with infected birds, consumption of raw poultry products, or hunting wild birds. These factors naturally put outdoor cats at higher risk.
While it is impossible to control HPAI in wild birds, which serve as a mobile reservoir for IAV genes, cats in endemic areas should be prevented from going outdoors, hunting, and feeding on raw meat.
A Fatal A/H5N1 Avian Influenza Virus Infection in a Cat in Poland. Microorganisms, 9 September 2023.