Puppies in pet stores appear to have transmitted a dangerous, antibiotic-resistant germ that's sickened 30 people across 13 states, the U.S. Centers for Disease Control and Prevention warned on Tuesday.

The infection in question is a multidrug-resistant form of Campylobacter jejuni, the agency said in a statement. So far, of 24 patients interviewed by the CDC, 21 (88%) said they had recently touched a puppy.

"Four people have been hospitalized," the CDC said, although "no deaths have been reported. Interviews with ill people and laboratory evidence indicate that contact with puppies, especially those from pet stores, is the source of this outbreak."

There's so far been no single supplier of puppies linked to the outbreak of the illness, although in 12 of 15 cases where people reported contact with a puppy at a pet store, that contact happened at one of the Petland chain of pet stores.

Illnesses have been reported from East to West — in Connecticut, Florida, Georgia, Illinois, Kentucky, Maryland, Minnesota, Nevada, Ohio, South Carolina, Tennessee, Utah and Wyoming.

"Campylobacter bacteria can spread to people through contact with poop of infected animals and contaminated food or water," the agency noted. Infection can be serious, involving diarrhea, fever and stomach cramps that begin two to five days after getting exposed to the germ. Most people do recover though, even without antibiotics.

"Puppies and dogs cancarryCampylobacter germs that can make people sick, even while appearing healthy and clean," the CDC noted. So, "people who own, work with or come in contact with puppies or dogs should take steps to stay healthy."

That means washing your hands well after touching puppies or dogs, their food or after you've cleaned up after the animals, the agency said.

The CDC notes that the strain of Campylobacter in this outbreak appears to be related to a strain that caused a similar outbreak of puppy-related human illness in 2016.

"The investigation is ongoing. CDC will provide updates when more information is available," the agency said.