Flu Mortality The flu causes an average of 36,000 deaths in the U.S. each year. During a regular flu season, about 90 percent of deaths occur in people 65 years and older. In spring 2009, a novel strain of influenza (pandemic H1N1) appeared and spread worldwide causing the first flu pandemic in more than 40 years. It is estimated that the 2009 H1N1 pandemic resulted in more than 12,000 flu-related deaths in the U.S. In contrast to seasonal flu, nearly 90 percent of the deaths occurred among people younger than 65 years of age. Overall, people between the ages of 50 and 64 were the hardest hit by 2009 H1N1 with about 80 percent of these people having one or more underlying health conditions.