In 2007, only two years after the 1918 flu sequence was completely decoded, influenza researcher Yoshihiro Kawaoka at the University of Tokyo and the University of Wisconsin described, in a paper in Nature, how he and his colleagues used the sequence to create live, infectious 1918 flu viruses. To demonstrate that these really were flu viruses, they infected 7 macaques with them. Not surprisingly, the macaques got severely ill, and the scientists eventually euthanized all of them.
Office of Strategic Communication