Avian Influenza Virus Infections in Felines: A Systematic Review of Two Decades of Literature

Abstract

As an avian influenza virus (AIV) panzootic is underway, the threat of a human pandemic is emerging. Infections among mammalian species in frequent contact with humans should be closely monitored. One mammalian family, the Felidae, is of particular concern. Domestic cats are susceptible to AIV infection and provide a potential pathway for zoonotic spillover to humans. Here, we provide a systematic review of the scientific literature to describe the epidemiology and global distribution of AIV infections in felines reported from 2004 to 2024. We identified 607 AIV infections in felines, including 302 associated deaths, comprising 18 countries and 12 felid species. We observed a drastic flux in the number of AIV infections among domestic cats in 2023 and 2024, commensurate with the emergence of H5N1 clade 2.3.4.4b. We estimate that this phenomenon is underreported in the scientific literature and argue that increased surveillance among domestic cats is urgently needed.

Keywords: One Health; avian influenza virus; cats; felines; zoonosis.

Figure 1.

PRISMA flow diagram for identification, screening, and review of the peer-reviewed scientific literature on avian influenza virus infections in felines published from 2004 to 2024. Abbreviation: PRISMA, Preferred Reporting Items for Systematic reviews and Meta-Analyses. Source: Page MJ, et al. BMJ 2021;372:n71. doi: 10.1136/bmj.n71.

Figure 2.

Number of peer-reviewed publications reporting avian influenza virus infections in felines each year from 2004 to 2024. Abbreviation: AIV, avian influenza virus.

Figure 3.

Number of avian influenza virus infections in feline species reported each year in the peer-reviewed literature, 2004–2024. The year published may not be representative of the year in which each of the reported AIV infections occurred. ^aA total of 147 AIV-associated tiger deaths were reported in 2005 from an H5N1 outbreak in a tiger zoo in Thailand in 2004. ^bApproximately 100 of 500 domestic cats sampled in Indonesia were reported to be seropositive for H5N1 (the cited official reports of these tests are difficult to find). ^cOutbreaks of H7N2 among domestic cats occurred in multiple US animal shelters, but data published in the peer-reviewed literature do not include the number of infections and thus they are not included in this figure. Abbreviation: AIV, avian influenza virus.

Figure 4.

Number of avian influenza virus–associated deaths in felines reported in the peer-reviewed literature, 2004–2024. The year published may not be representative of the year in which each of the reported AIV-associated deaths occurred. One hundred forty-seven AIV-associated tiger deaths were reported in 2005 from an H5N1 outbreak in a tiger zoo in Thailand in 2004. Abbreviation: AIV, avian influenza virus.

Figure 5.

Geographical distribution of avian influenza virus infections reported in feline species, 2004–2024. Abbreviation: AIV, avian influenza virus.