Depends on how fresh it is. Which is why sushi and very especially, raw beef is a lot safer than people assume :)
If you've got it lying around your fridge for a couple of weeks then it's a lot more questionable than something you've just bought. For example, raw chicken GOES BAD (in my country at least) within 48 hours of being refrigerated, so you gotta cook all of it and freeze some or eat it all :P.
Most sushi places only order a certain amount of sushi a day, and finish with little or no waste, and the staff have a set-lunch sushi for lunch break and/or dinner break. I believe fish keeps slightly better than chicken, but I'm sure those places know what they're doing, lest somebody gets sick.
It does happen, but it's just food poisoning from a bad clam. Salmonella is technically food poisoning, because I read that only older, immunocompromised people died from it.
BON APPETIT~ <3