A small but growing number of house cats have gotten sick from H5N1, the bird flu strain driving the current U.S. outbreak.

The variant of bird flu that killed a Louisiana resident has now been found in dairy cows. Until now, the human cases of bird flu traced to cattle have been mild, mostly eye infections. But the U.S. Department of Agriculture confirmed that a strain previously found only in wild birds has turned up in dairy herds in Nevada ‒ raising concerns that future human infections could be more serious.

Three of America’s top milk-producing states are not participating in the U.S. Department of Agriculture’s program designed to catch the spread of the virus.