WHO: statement and risk assessment on H5N1 In Cats in Poland
On June 27, 2023, Poland's IHR National Focal Point notified the World Health Organization (WHO) about an unusual increase in cat deaths across the country. As of July 11, a total of 47 samples from 46 cats and one caracal were tested, with 29 samples (62%) testing positive for influenza A(H5N1). The positive samples were found in 13 different areas of Poland. Some cats displayed severe symptoms like breathing difficulties, bloody diarrhea, and neurological signs, leading to rapid deterioration and death. Out of the cats tested, 20 showed neurological signs, 19 had respiratory signs, and 17 displayed both. Fourteen cats were euthanized, and an additional 11 died. Post-mortem examinations suggested pneumonia as the cause of death in some cases. Genetic analysis revealed that the 19 sequenced viruses belonged to the H5 clade 2.3.4.4b and were closely related to each other and to the H5N1 viruses circulating in wild birds and causing outbreaks in poultry in Poland. The source of the virus exposure in cats is currently unknown. Possible sources of infection include direct or indirect contact with infected birds or their environments, consumption of infected birds, or ingestion of food contaminated with the virus. Among the available information for 25 cats, two were outdoor cats, 18 were indoor with access to outdoor spaces, and five were strictly indoor cats. Seven cats had the opportunity for contact with wild birds. This is the first reported instance of widespread avian influenza A(H5N1) infection in cats within a single country. Previous cases of A(H5N1) infection in domestic cats were sporadic and occurred through close contact with infected birds or consumption of infected bird meat.
Since late 2021, numerous outbreaks of H5N1 in poultry and wild birds have been reported worldwide, with clade 2.3.4.4b viruses becoming dominant in Asia, Europe, the Americas, and Africa. These viruses have also been detected in non-avian species, including wild terrestrial and marine mammals, possibly through contact with infected birds or their environments.
Since 2020, 12 human cases of avian influenza A(H5N1) clade 2.3.4.4b have been reported to the WHO, with four being severe and eight mild or asymptomatic. The exact source of mild or asymptomatic cases is unclear. Most human infections with A(H5N1) result from contact with infected live or dead poultry and can lead to severe illness and death. As of July 12, 70 individuals who had contact with confirmed cats have completed self-monitoring without reporting any symptoms. As of now, no human infections resulting from contact with infected cats have been reported. The risk of human infections at the national level is assessed as low for the general population and low to moderate for cat owners and those occupationally exposed to infected cats without appropriate personal protective equipment.
