Study of avian flu in cats suggests heightened zoonotic pandemic risk

Prevalence of H5N1 avian flu in cats shows risk of emerging threat to humans

Springtime patterns of avian migration – alongside the rapidly evolving H5N1 variant of avian flu – have raised the risk of a future human pandemic. Researchers from the University of Maryland, School of Public Health have published a study in on the spread of avian flu in cats and are now calling for urgent surveillance of the feline disease to mitigate the virus developing the ability for direct human-to-human transmission.

“The H5N1 virus has evolved, and the way that it jumps between species – from birds to cats, and now between cows and cats, cats and humans – is very concerning.

“As summer approaches, we are anticipating [more] cases on farms and in the wild to rise again,” said Dr. Kristen Coleman, assistant professor in UMD School of Public Health’s Department of Global, Environmental and Occupational Health and affiliate professor in UMD’s Department of Veterinary Medicine, and lead author of the paper.  

“Avian flu is very deadly to cats, and we urgently need to figure out how widespread the virus is in cat populations to better assess spillover risk to humans,” she said.

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The global review of research papers – published between 2004 and 2024 – found 607 recorded avian flu infections in cats, resulting in 302 associated deaths, across 18 countries and in 12 feline species, from pet cats to tigers. Cats have not been actively monitored for avian flu and any testing is only performed postmortem, if at all. Considering the lack of surveillance infrastructure these numbers are likely to be a significant underestimate, Coleman said. 

The study has shown that cats have been contracting avian flu directly by eating infected birds or contaminated raw chicken feed, but also indirectly through contact with other mammals – for example, farm cats drinking raw milk from infected cows, between pet cats, and likewise tigers to other tigers. 

Infected cats often suffer from acute encephalitis – brain swelling – alongside severe symptoms which are often mistaken for rabies. H5N1 is the most-deadly strain of avian flu and is highly infectious, making up the majority of cases in domestic cats, with a fatality rate of 90%. Avian flu in humans is less deadly, but has killed around half of the 950 people it has infected, globally.

Dr. Coleman and her team are concerned about the risk posed by avian flu getting into animal shelters which could result in large outbreaks that could potentially involve humans. An event like this happened in New York City with a different strain of avian flu in 2016.

“Our future research will involve studies to determine the prevalence of HPAI and other influenza viruses in high-risk cat populations such as dairy barn cats. Our research seeks to protect people and our vulnerable pet cats from the emerging threat of H5N1,” said Ian Gill Bemis, doctoral student studying avian flu in cats and coauthor of the paper.

While to date there have been no reported cases of human-to-human transmission of avian flu, researchers remain concerned that as the virus spreads and evolves, it could become more easily transmissible as an airborne pathogen. 

For further reading please visit: https://doi.org/10.1093/ofid/ofaf261