Just off the top of my head…What I learned when we went through the Teenage Ninja Turtle craze at this house, which ended with me doing a fair amount of research on this (and buying a Painted Turtle, Chrysemys picta, but that’s another story.)
The increased salmonella risk was due to people breeding water turtles like Painted Turtles and Red Sliders (as distinguished from “tortoises”) by the tens of thousands to fill the market need for “cute lil baby turtles” the size of a 50 cent piece. Crowded together in large tanks, they were a perfect bacteria breeding ground. And yes, kids got sick. Not sure about the actual death toll, but yeah, it was a genuine problem.
Changing the laws in the mid-1970s to prohibit the sale of turtles less than 4" in shell diameter fixed this problem, since it takes several years for a turtle to get this big. This cut out the whole “cute lil baby turtle” market altogether, and people stopped breeding them by the tens of thousands, so the huge salmonella contamination problem, Stateside at least, pretty much went away.
Of course, the rules on breeding turtles by the thousands don’t apply to Asia. I have no clue how the laws read now vis-a-vis importing Red Sliders and Painted Turtles into the U.S. from Asia.
Still, there is apparently a risk of salmonella in any reptile feces–turtle, tortoise, snake, lizard. I’m not sure why this is, but over the years we’ve had water turtles, box turtles, and snakes at our house, and the health care information has always said the same thing: “Always have the kid wash his hands after handling his pet, and after cleaning the cage/tank.”
Also, never allow your reptile to bathe in the family bathtub, since if he poops in there, it’s thereby considered to be contaminated with salmonella.
But turtles are kewl.
Don’t worry about the bugs too much, let the kids have a good time. Just have 'em wash their hands afterwards. And keep Turtle out of the swimming pool, too.
Can’t address the “bought illegal pets over the Internet” thing, as it’s none of my business. 