Bird flu infections in cats are not being tracked or managed seriously enough, according to a new study by researchers at the University of Maryland. With the highly pathogenic avian influenza virus (H5N1) spreading in the U.S., scientists say the growing number of feline cases could increase the risk of human transmission.
“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,” said Kristen Coleman, an airborne infectious disease expert and co-author of the study.
As birds migrate across the U.S. during spring, there is a higher chance of the virus spreading, especially to farms and wild areas. Coleman and fellow researcher Ian Bemis reviewed studies from 2004 to 2024 and identified 607 reported cases of bird flu in cats across 18 countries. Of those, 302 infections were fatal.
Most of these cases were linked to the H5N1 clade 2.3.4.4b strain, which had a 90% death rate among the reported infections. However, the researchers believe many more cases are going undetected, and the real fatality rate could be lower due to underreporting and limited testing.
The team urges veterinarians, public health officials, and pet owners to step up surveillance efforts, especially for outdoor and farm cats that may come into contact with infected birds or raw animal products.
Though no cat-to-human transmission has been confirmed for this strain, a 2016 outbreak of a different strain in New York City shelters did result in a case of human infection from cats. Experts warn that just a few genetic changes in the virus could make human-to-human transmission possible.
“Owners of farm cats, free-roaming cats, shelter workers, and veterinarians may be at higher risk of exposure,” said Coleman.
Cats can contract the virus by eating infected wild birds or animals, consuming contaminated raw food or milk, or through contact with other infected animals. Hunting is a natural behavior for cats, with free-roaming cats killing an estimated 186 animals per year on average. The study suggests this could be another reason to keep cats indoors—not just to protect wildlife, but to reduce disease risk.
Future research by the Maryland team will focus on testing cats in high-risk environments, like dairy farms, for bird flu and other viruses.
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