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Review article - Peer-reviewed, 2021

Influenza Virus Infections in Cats

Frymus, Tadeusz; Belak, Sandor; Egberink, Herman; Hofmann-Lehmann, Regina; Marsilio, Fulvio; Addie, Diane D.; Boucraut-Baralon, Corine; Hartmann, Katrin; Lloret, Albert; Lutz, Hans; Pennisi, Maria Grazia; Thiry, Etienne; Truyen, Uwe; Tasker, Severine; Moestl, Karin; Hosie, Margaret J.


In the past, cats were considered resistant to influenza. Today, we know that they are susceptible to some influenza A viruses (IAVs) originating in other species. Usually, the outcome is only subclinical infection or a mild fever. However, outbreaks of feline disease caused by canine H3N2 IAV with fever, tachypnoea, sneezing, coughing, dyspnoea and lethargy are occasionally noted in shelters. In one such outbreak, the morbidity rate was 100% and the mortality rate was 40%. Recently, avian H7N2 IAV infection occurred in cats in some shelters in the USA, inducing mostly mild respiratory disease. Furthermore, cats are susceptible to experimental infection with the human H3N2 IAV that caused the pandemic in 1968. Several studies indicated that cats worldwide could be infected by H1N1 IAV during the subsequent human pandemic in 2009. In one shelter, severe cases with fatalities were noted. Finally, the highly pathogenic avian H5N1 IAV can induce a severe, fatal disease in cats, and can spread via cat-to-cat contact. In this review, the Advisory Board on Cat Diseases (ABCD), a scientifically independent board of experts in feline medicine from 11 European countries, summarises current data regarding the aetiology, epidemiology, pathogenesis, clinical picture, diagnostics, and control of feline IAV infections, as well as the zoonotic risks.


cats; influenza A virus; low pathogenic; highly pathogenic

Published in

2021, volume: 13, number: 8, article number: 1435
Publisher: MDPI

Authors' information

Frymus, Tadeusz
Warsaw University of Life Sciences
Belák, Sándor (Belak, Sandor)
Swedish University of Agricultural Sciences, Department of Biomedical Science and Veterinary Public Health
Egberink, Herman
Utrecht University
Hofmann-Lehmann, Regina
University of Zurich
Marsilio, Fulvio
University of Teramo
Addie, Diane D.
No organisation
Boucraut-Baralon, Corine
Hartmann, Katrin
University of Munich
Lloret, Albert
Autonomous University of Barcelona
Lutz, Hans
University of Zurich
Pennisi, Maria Grazia
University of Messina
Thiry, Etienne
University of Liege
Truyen, Uwe
Leipzig University
Tasker, Severine
University of Bristol
Moestl, Karin
University of Veterinary Medicine Vienna
Hosie, Margaret J.
University of Glasgow

UKÄ Subject classification

Clinical Science

Publication Identifiers


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