Two pet cats in New York City died after being infected with bird flu, health officials said on Friday, a sign of the increased spread of a virus that has decimated chickens and cattle and sickened dozens of people nationally.
It was unclear how the cats had been infected. Potential sources of the virus include unpasteurized milk, infected food and exposure to infected birds. The officials did not immediately disclose when the cats became infected and died.
The discovery of bird flu in the cats raises concerns in a city where hundreds of thousands of pet and feral cats live, although the immediate threat to people remained low, health officials said.
In 2016, a veterinarian was infected with bird flu after having contact with a sick cat at a Manhattan animal shelter. The type of flu in that case was far less severe than the H5N1 bird flu viruses that have infected wild and domestic birds and cattle herds in the United States for more than a year.
“Bird flu viruses present a wider risk to the general public only if the virus develops the ability to transmit between people, which we have not seen,” the city’s acting health commissioner, Dr. Michelle Morse, said in a statement.
Nationwide, more than 100 domestic cats are known to have been infected with bird flu since 2022. Dead cats found on dairy farms have sometimes been the first sign that the virus was tearing through cattle herds.
In New York State, the H5N1 virus has infected a number of wild mammals, including foxes and an eastern gray squirrel.
In New York City, the virus has killed wild birds, including red-tailed hawks and Canada geese, as well as poultry for sale at live bird markets. Ducks at the Queens Zoo and birds at the Bronx Zoo have also died after being infected.
Public health experts worry that the more widely H5N1 circulates among mammals, the more likely it is to ignite a pandemic among humans. In recent months, some experts have expressed concern that domestic cats could provide a major avenue for the evolution of the H5N1 virus. The fear is that as H5N1 circulates in cats or other mammals, it will mutate or swap genes with another flu virus, resulting in a virus that spreads more easily among people.
In the past, such viruses have killed about half the people known to be infected. But recent influenza cases related to the H5N1 virus have proved far less severe in humans. More than 60 people have been diagnosed with the illness in the current U.S. outbreak; one has died.
New York City health authorities are investigating how the cats that died might have become infected. A health department spokeswoman, Chantal Gomez, said one of the cats was owned by a veterinarian. She said that testing had confirmed that one of the cats had H5N1. Further testing was needed to confirm which subtype of bird flu had infected the second cat.
A 2012 analysis by the city’s Economic Development Corporation estimated that there were about 500,000 domestic cats in the five boroughs. The number of feral cats in the city has exploded in recent years as many people who got pets during the coronavirus abandoned them.