The Centers for Disease Control and Prevention (CDC) keeps a Most Wanted list for flu viruses. The agency evaluates every potentially dangerous strain, and gives them two scores out of 10—one reflecting how likely they are to trigger a pandemic, and another that measures how bad that pandemic would be. At the top of the list, with scores of 6.5 for emergence and 7.5 for impact, is H7N9.
Office of Strategic Communication