"The Spanish flu remains the most deadly flu pandemic to date by a long shot, having killed an estimated 1% to 3% of the world's population. The most recent comparable flu pandemic occurred in 2009 to 2010, after a new form of the H1N1 influenza strain appeared. The disease was named the "swine flu" because the virus that causes it is similar to one found in pigs (not because the virus came from pigs). The swine flu caused respiratory illnesses that killed an estimated 151,700-575,400 people worldwide in the first year, according to the Centers for Disease Prevention and Control. That was about 0.001% to 0.007% of the world's population, so this pandemic was much less impactful than the 1918 Spanish flu pandemic. About 80% of the deaths caused by swine flu occurred in people younger than 65, which was unusual. Typically, 70% to 90% of deaths caused by seasonal influenza are in people older than 65. A vaccine for the influenza strain that causes swine flu is now included in annual flu vaccines. People still die from the flu every year, but the numbers are far lower, on average, compared to those for the swine flu or Spanish flu pandemics. Annual epidemics of seasonal flu result in about 3 million to 5 million cases of severe illness and about 290,000 to 650,000 deaths, according to the World Health Organization."