There have been reports of people getting sick from a disease called Anisakiasis this is a parasitic disease caused by nematodes ( worms) that attach to the wall of the stomach or intestine. This is very common when the fish or sushi is not cooked all the way and when you ingest those parasites they quickly taken over our stomachs which leads to irritating it, fevers and vomiting. So just make sure your sushi chef is getting fully cooked sushi.