The Flu Has Been Making People Sick for At Least 500 Years

There’s no doubt about it—flu season is here.The offending strain this year—to blame for about 95 percent of cases—is H3N2, which is bad news for anyone hoping that the flu shot might guarantee an infection-free winter. Thanks to a virus mutation that occurred after the shot was manufactured, this year’s vaccine is believed to be only 33 percent effective at preventing the flu. It is hard to talk about the flu without mentioning the most deadly of all flu pandemics—and the most deadly of all disease outbreaks in history—the 1918-1919 “Spanish flu.” The pandemic got its name from the erroneous assumption that the disease originated in Spain, but it killed up to 50 million people around the world. Scientists believe the Spanish flu may actually have first emerged in China, but there's not full agreement on that. What we’re surer of, however, is that the virus—or at least variations of it—has been around for hundreds of years.