Even though tiny turtles were banned as pets more than 30 years ago, they were apparently to blame for a large salmonella outbreak in 2007 and 2008. Sickened were 107 people, mostly children, in 34 states. One-third of the victims were hospitalized.

Two of the children who became sick had gone swimming with their pets in a backyard pool, according to the report in this month's Pediatrics. Health officials began their investigation in the fall of 2007 after a North Carolina teen and a pal from South Carolina swam in an unchlorinated pool with two pet turtles. Both girls developed bloody diarrhea, vomiting, fever and stomach cramps; one developed kidney failure and spent eight days in the hospital.

"It's very easy to think of turtles as being a very gentle and nice pet," but many carry salmonella, without showing any signs, Julie Harris, a scientist at the federal Centers for Disease Control and Prevention and the report's lead author, told the Associated Press.

The Food and Drug Administration banned selling turtles with shells less than four inches long in 1975 because of the public health impact of turtle-associated salmonellosis. Despite the ban, in recent years, several widespread outbreaks of salmonella infection related to undersized turtles have been reported to the Centers for Disease Control and Prevention. And, according to the American Veterinary Medical Association, the number of pet turtles is actually increasing—from 950,000 in 1996 to almost 2 million in 2006.

All reptiles (turtles, lizards, snakes) and amphibians (frogs, salamanders) are commonly contaminated with salmonella. The bacteria do not make these animals sick, but they can make people ill and even be life-threatening to children, elderly people, and others with weakened immune systems. Small pet turtles are of particular concern because children are more prone to handling the turtles without washing their hands afterward, and sometimes even put the turtles in their mouths.

In the outbreak documented in Pediatrics, the same strain of salmonella found in the teenage girls was also found in more than 100 other people in 34 states who were reported ill between early May 2007 and mid-January 2008, according to the CDC. When 80 of these people were questioned, 47 of them confirmed that they had been exposed to a turtle during the seven days before they got sick.

When it can track sellers down the FDA, together with related agencies, has pursued criminal charges. In a recent case, Strictly Reptiles of Hollywood, Florida was convicted and sentenced in July 2008 for its role in illegally selling more than 1,000 live undersized turtles.