An increasing number of cats are being infected with avian influenza (bird flu), causing health officials to panic about a possible human pandemic. University of Maryland scientists are now calling for increased surveillance of avian flu in domestic cats.

11 Cats In Colorado Test Positive For Bird Flu As More Cat Food Is Recalled

This surveillance increase comes after a global review of 20 years of published data reveals a dramatic uptick in feline infections, and the number of ways cats are being infected, after the emergence of H5N1 clade 2.3.4.4b in other mammals.

“Infections among mammalian species in frequent contact with humans should be closely monitored,” the researchers wrote yesterday in Open Forum Infectious Diseases, according to a report by CIDRAP, The University of Minnesota’s news outlet. “Domestic cats are susceptible to AIV [avian influenza virus] infection and provide a potential pathway for zoonotic spillover to humans.”

“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,” which was consistent with the emergence and increased transmission of the clade in birds and mammals, the authors of the research said. “Interestingly, cases of H5N1 clade 2.3.4.4b recently reported by the Colorado Health Department included two indoor-only domestic cats with no known exposure to infected animals. This observation raises concerns regarding new and unknown transmission routes of AIV to domestic cats.”

“The infection of ruminants rules out the predation or scavenging route of transmission in this case and suggests that other routes of transmission are occurring, in addition to cattle-to-cattle transmission,” they added.

So far, the avian influenza has infected only 950 people worldwide, but has killed about half of them. From April 2022 (when cumulative data on US human cases started being collected) to January 2025, the United States has recorded 66 human infections and 1 death, the researchers noted.

First U.S. Human Bird Flu Death Reported

The increase in infections among cats may be attributed to exposure to wild birds. However, indoor cats that had never contacted wild birds have also been infected with avian influenza, puzzling health officials.

“Indoor Only” Cats Test Positive For Bird Flu