“Nightmare bacteria” with unusual resistance to antibiotics of last resort were found more than 200 times in the United States last year in a first-of-a-kind hunt to see how much of a threat these rare cases are becoming, health officials said Tuesday.

That’s more than they had expected to find, and the true number is probably higher because the effort involved only certain labs in each state, officials say.

The problem mostly strikes people in hospitals and nursing homes who need IVs and other tubes that can get infected. In many cases, others in close contact with these patients also harbored the superbugs even though they weren’t sick – a risk for further spread.

Some of the sick patients had traveled for surgery or other health care to another country where drug-resistant germs are more common, and the superbug infections were discovered after they returned to the U.S.

“Essentially, we found nightmare bacteria in your backyard,” said Dr. Anne Schuchat, principal deputy director of the U.S. Centers for Disease Control and Prevention.

“These verge on untreatable infections” where the only option may be supportive care – fluids and sometimes machines to maintain life to give the patient a chance to recover, Schuchat said.