"I would not go to a restaurant with a 'C' rating in New York largely for this reason. It's a big red flag when a sushi restaurant can't maintain an 'A' rating, because one of the main things they get rated on is refrigeration. They're not cooking the fish so that is the only prevention method, keeping it cold," Dr. Daniel Eiras, assistant professor of infectious diseases at NYU Langone Medical Center, told CBS News last May.