Dog lovers beware: Federal health officials are warning that puppies, particularly those found in pet stores, are once again behind an outbreak of a nasty stomach bug that can cause bloody diarrhea.

The yucky culprit is a bacteria called Campylobacter jejuni. It’s one of the most common bacterial causes of diarrhea worldwide, often accompanied by symptoms of fever and stomach cramps. Though most cases are relatively mild and self-limiting, it can take up to a week for our bodies to clear the infection.

According to the Centers for Disease Control and Prevention, at least 30 people in 13 states have gotten sick with the same strain of C. jejuni implicated in the outbreak, as of December 17. While four people have been hospitalized, none have died. Nearly all of the interviewed victims (21 out of 24) remembered visiting and touching puppies soon before their symptoms began.

Of these encounters, 15 people had touched puppies at a pet store and 12 had done so at a Petland store. Five were Petland employees. Most damning is that the specific strain of C. jejuni found in these people bears a close genetic resemblance to the strain that sickened 113 people in an outbreak that lasted from 2016 to 2018 and was also linked to pet store puppies. In another troubling sign of the times, both strains are resistant to the front-line antibiotics used to treat more serious cases.

While infected dogs can show similar symptoms as people, especially if they’re puppies, they can also spread the disease while appearing perfectly healthy. So the CDC recommends that anyone handling dogs and puppies should thoroughly wash their hands afterward. New dog owners should also schedule a check-up within a few days and immediately take the dog to the vet if it shows any signs of illness, including acting sluggish, not eating, and having diarrhea.

Another recommended piece of advice by the CDC is that people avoid having dogs lick their mouths and faces, though that advice is probably much harder to follow.