A salmonella outbreak has been linked to small turtles, the Centers for Disease Control and Prevention announced Thursday. So far, 15 people have been sickened across 11 states, with five requiring hospitalization.

“Many people in this outbreak reported purchasing turtles with shells less than 4 inches long from online stores before getting sick,” the CDC said. It noted that three of the people who were sickened purchased turtles from the website myturtlestore.com.

The CDC notes that it is illegal to sell turtles that small, but that does not always stop websites and certain physical locations, like flea markets and roadside stands.

People can get salmonella by touching a turtle or something in its environment, and then touching their mouth or handling food without washing their hands first, the CDC said.

The CDC also notes that pet turtles of any size can carry salmonella, even if they appear healthy and clean.

To avoid getting sick, the CDC recommends washing your hands after handling and feeding pet turtles, and to avoid kissing or snuggling the animals. The CDC also advises people not to eat around their pet turtles.

The CDC said you should seek medical attention if you experience severe symptoms, which include a fever over 102 degrees Fahrenheit, diarrhea that lasts more than 3 days without improving, and excessive vomiting.