A major study warns that cats need to be monitored more closely as bird flu-carrying birds migrate across the world and pose a greater threat of human-to-human transmission.
In recent years, we have seen the H5N1 strain of the bird flu virus rapidly evolve to the point where it can now infect multiple non-human species. As this panzootic process – a widespread disease outbreak affecting many different species across a wide geographical range – is underway, the threat to humans continues to grow.
We have already seen that various mammal species that have frequent contact with humans have begun to contract the infection, so there is a need for greater monitoring of these species. However, one species that is of particular concern is the household cat.
Cats have proven themselves to be susceptible to avian influenza infection and serve as a potential pathway for spillover into humans. Both domestic cats and larger cat species have been known to contract the disease.
“The 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 cases on farms and in the wild to rise again,” Dr Kristen Coleman, assistant professor in the University of Maryland (UMD) School of Public Health’s Department of Global, Environmental and Occupational Health and affiliate professor in UMD’s Department of Veterinary Medicine, explained in a statement.
“Bird 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 added.
“We want to help protect both people and pets.”
Coleman and Ian Gill Bemis, co-author of the paper and doctoral student studying bird flu in cats, undertook a major global review of research papers documenting cases of bird flu in cats published between 2004 and 2024. They found 607 bird flu infections of cats across 18 countries, which were associated with 302 deaths. These infections occurred in 12 cat species, from domestic cats to tigers.
Despite their propensity for catching bird flu, cats are not actively monitored for the disease and any testing typically happens postmortem, if it happens at all. As such, it is probable that the numbers of infections are significantly higher than the research has shown.
More worrying still is the variety of ways that cats can contract the disease. The most obvious route that springs to mind is probably cats killing and eating birds, but they can also get it from contaminated raw chicken feed, or even indirectly from other mammals. For instance, farm cats can pick it up from infected cows if they drink raw milk, while pet cats can come into contact with other contaminated cats, just as tigers can get it from other tigers.
When infected, cats tend to suffer acute encephalitis (brain swelling) and other severe symptoms that can be mistaken for signs of rabies, the authors note. The deadliest strain of bird flu is highly infectious and makes up the majority of cases in domestic cats, with a current fatality rate of 90 percent. At the moment, bird flu in humans is less deadly, but it has still killed about half of the 950 people who have caught it across the globe.
Between April 28, 2022 and May 7, 2025, the US had 70 confirmed cases of human infection and one death.
At present, there have not been any reported cases of human-to-human transmission of bird flu, but the Coleman and Bemis worry that this may change as the virus continues to spread and evolve.
“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,” Bemis added.
The study is published in the journal Open Forum Infectious Diseases.
Source Link: 20 Years Of "Very Concerning" Data Concludes Cats Can Catch Bird Flu And Could Pass It To Humans
