(NewsNation) — Public health officials with the Centers for Disease Control (CDC) are investigating a multistate salmonella outbreak reportedly linked to tiny turtles with shells 4 inches long or less.

At least 51 people across 21 states have contracted the illness, and 23 of those infected have been hospitalized.

The outbreak under investigation is mostly impacting young children: 17 of those ill are under 5 years old, and 10 children are less than 1.

Federal law bans sale of tiny turtles

According to federal law, the sale and distribution of small turtles with shells less than four inches long is illegal because the reptiles can cause illness, especially in little kids, the CDC said.

However, several retail shops online, in-store and on the side of the road still sell these animals as pets despite the ban.

Health officials recommend Americans only buy turtles that have shells longer than four inches and from a reputable business or rescue. The CDC also recommends avoiding having pet turtles for children under 5 years old or adults 65 years or older due to their weakened immune systems.

Salmonella symptoms

Most people who contract salmonella will experience a fever and stomach cramps after being exposed to the bacteria. This will also lead to the development of diarrhea.

It usually lasts between four to seven days, and many recover from the illness without treatment.

However, some people might experience severe symptoms that would cause them to be hospitalized, the CDC said. Severe symptoms include having diarrhea for more than three days, bloody stool, endless vomiting and signs of dehydration, which include not peeing as much, dry mouth or throat and feeling lightheaded when standing up.