BIRD FLU IN CATS POINTS TO RISK OF ANOTHER PANDEMIC

As spring brings migrating birds back into motion, another movement is raising alarm: the rapid evolution of bird flu (H5N1), now edging closer to a potential human pandemic.

Researchers from the University of Maryland School of Public Health have published a sweeping review of bird flu infections in cats, urging immediate surveillance to prevent the virus from jumping from animals to humans.

The study, published in Open Forum Infectious Diseases, reviews two decades of global data and highlights a troubling pattern.

“The virus has evolved in worrying ways. It’s now jumping between species—birds to cats, cows to cats, even cats to humans,” said Dr. Kristen Coleman, lead author and assistant professor at the UMD School of Public Health. “As we head into summer, we expect to see more cases on farms and in the wild. We need to act fast to protect both people and pets.”

A Silent Spread

Between 2004 and 2024, researchers documented 607 cat infections from bird flu across 18 countries and 12 feline species—including pet cats, stray cats, and even tigers. More than 300 of those cases were fatal. But the true number is likely much higher, Coleman warns, since cats aren’t routinely tested for bird flu. Most cases are only identified after death.

Cats can contract the virus in several ways: by eating infected birds or raw poultry, drinking contaminated raw milk from infected cows, or through contact with other infected animals. Some cases have involved cat-to-cat transmission—raising further concerns about viral adaptation.

Infected cats often develop acute encephalitis (brain swelling) and other severe symptoms that are sometimes mistaken for rabies. The strain most often found in cats is highly pathogenic and deadly, with a 90% fatality rate among those infected.

A Warning Sign for Humans

While bird flu in humans is less common, it remains deadly—killing roughly half of the nearly 950 people infected globally. In the United States, 66 human cases and one death have been recorded between April 2022 and January 2025.

“There’s currently no confirmed human-to-human transmission,” said Coleman. “But the more this virus spreads and mutates across species, the more likely it is to evolve into something more dangerous—and more transmissible.”

Researchers are especially worried about outbreaks in places like animal shelters, where many cats live in close quarters. A large-scale transmission event involving people is not out of the question. A similar outbreak occurred in New York City in 2016, involving a different strain of bird flu, and raised serious concerns about public health risks.

Urgent Need for Surveillance

To better understand and contain this emerging threat, Coleman and her team are calling for focused surveillance of high-risk cat populations, such as barn cats on dairy farms.

“Our future research will target how widespread H5N1 and other flu viruses are among cats in high-risk settings,” said co-author Ian Gill Bemis, a doctoral student at UMD. “Our goal is to protect both human health and the welfare of our vulnerable pet cats.”

As bird flu continues to evolve, experts say keeping an eye on cats could be key to preventing the next pandemic.