Going to the hospital is supposed to be good for you. But in an alarming number of cases, it isn't. And often it's fatal. In fact it is the most dangerous thing most people will do. Until very recently, health care experts believed that preventable hospital error caused some 98,000 deaths a year in the United States — a figure based on 1984 data. But a new report from the Journal of Patient Safety using updated data holds such error responsible for many more deaths — probably around some 440,000 per year. That's one-sixth of all deaths nationally, making preventable hospital error the third leading cause of death in the United States.