Citing the "unprecedented crisis" of bats dying off from West Virginia to New England, federal officials are asking people to stay out of all caves in states struck by "white-nose syndrome."

The U.S. Fish and Wildlife Service made the unusual request Thursday to guard against the possibility people are unwittingly spreading the mysterious affliction when they explore multiple caves. There is no evidence that white nose is a threat to people.

White nose has been confirmed in eight states this winter. It's named for the white smudges of fungus on the noses and wings of hibernating bats.

Researchers suspect a fungus that thrives in cold, moist caves causes white nose, and that it's primarily spread from bat to bat.