The ongoing spread of bird flu in the United States has alarmed experts—not just because of human cases causing severe illness, but also due to troubling new instances of infections in cats.

Though cases of infection are rare, cats seem especially susceptible to the bird flu virus, or Type A H5N1. Even before the cattle outbreak, there were feline cases linked to wild birds or poultry. Since March, dozens of cats have caught the virus. These include barn and feral cats, indoor cats, and big cats in zoos and in the wild.