Sushi is prepared using vinegar in the rice. The vinegar has properties of killing any bacteria that may be in the fish. Also, it is usually consumed with Saki, which also works to immunize the body against bacteria in the fish.
Also, contrary to popular belief, fresh fish is almost never used in sushi because there is no way to kill the bacteria. Instead, sushi-grade fish is blast-frozen on the boat as soon as it is caught. It is usually frozen colder than a normal freezer and left that way for a few days. Then, when it is time to be used, it is quickly thawed with minimal air contact.
You should NOT have to worry about getting sick from sushi. Restaurants that prepare sushi have the experience to handle it properly. You would be much more likely to get sick from raw oysters at a bar that doesn't have the facilities to prepare raw seafood.