U.S. health officials are worried about a new gene that can turn many types of bacteria into superbugs that are able to resist nearly all antibiotics.

The Centers for Disease Control and Prevention reports that patients in three states - California, Massachusetts and Illinois - were infected with different types of bacteria that contain the gene.

All had recently been in India, where the problem is thought to be widespread.

Two cases also have turned up in Canada. Doctors described them Monday at an infectious diseases conference in Boston.