Multi-drug resistant infections reported across 13 U.S. states have been linked to contact with puppies, particularly puppies at pet stores, the Centers for Disease Control and Prevention (CDC) said Tuesday. The infections are caused by a bacteria known as Campylobacter that can cause diarrhea, fever and abdominal cramps.

Campylobacter causes an estimated 1.5 million illnesses in the U.S. every year and is typically acquired by eating raw or undercooked poultry, according to the CDC. The strain isolated in this outbreak is resistant to commonly recommended, first-line antibiotics.

Infections were reported in 30 people from January 6 through November 10, according to the CDC. Four of them have been hospitalized, and no deaths have been reported. The largest number of cases was recorded in Minnesota, with 6, followed by Ohio with five cases and Nevada with four.

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The CDC said 15 out of 24 people who were interviewed reported having contact with a puppy at a pet store, and 80 percent of those people reported a link to Petland, a pet store chain.

The chain does not have stores in states where more than a third of the cases were reported.

The chain estimates that more than 2.4 million "customer socializations" of Petland puppies occurred during the latest outbreak period, according to statement from Petland released on Tuesday ahead of the CDC report.

"Petland takes the health and welfare of our employees, our customers and our pets very seriously. Since an earlier outbreak in 2016, in which no specific source of infection was identified, Petland has implemented all recommended protocols from federal and state animal and public health officials to prevent human and puppy illness," said the statement.

In September last year, the CDC reported that contact with puppies at half a dozen pet store companies across 18 states led to infections in 118 people from January 2016 through February 2018. No single breeder or distributor was found to be the source of that outbreak, but the CDC said in a 2018 report that "epidemiologic and laboratory evidence indicated that contact with puppies sold through Petland stores were a likely source of this outbreak."

The CDC recommends people take the following precautions to protect themselves while visiting with dogs:

Wash your hands thoroughly after touching dogs, their poop, or their food. Take extra care that children playing with the puppies also wash their hands carefully.

Pick up and dispose of dog poop, especially in areas where children might play.