Why don't people?get food poisoning by eating sushi if its raw fish?

Sushi contamination: People can get food poisoning from any fish that isn't fresh, just like they can get it from any food left out too long. Raw fish can also carry parasites, like raw meat can. That's why we learned to cook foods, one has to presume. Just googling sushi safety brings up salmonella and botulism reports. http://chicago.cbslocal.com/2011/10/27/2-investigators-is-your-sushi-safe/.