A multi-state salmonella outbreak linked to tiny turtles has sickened dozens of people in 21 states, including Illinois, federal officials said.

According to the Centers for Disease Control and Prevention, 51 people have gotten sick after coming into contact with small turtles with shells less than four inches long. Of those who’ve become sick, two people are from Illinois and another two reside in Indiana.

Seventeen of those affected, approximately 33%, are under 5 years old, and 10 of those who’ve gotten ill are under one year old.

The sale and distribution of turtles with shells less than four inches long is banned under federal law because of repeated illnesses and outbreaks, according to the CDC. Some online retailers, pet stores and roadside markets still sell the turtles even with the ban in place.

The CDC warns that pet turtles of any size can carry salmonella germs in their droppings even if they look healthy and clean. These germs can easily spread to their bodies, tank water, and anything in the area where they live and roam.

Pet turtles are not recommended for children younger than 5, adults aged 65 and older, and people with weakened immune systems who are more likely to become seriously ill.

Salmonella illness usually lasts 4 to 7 days, and most people recover without treatment, health officials said. Most people who are infected develop diarrhea, fever, and stomach cramps 6 hours to 6 days after being exposed to the bacteria.