This encore program follows scientists, led by Jeffrey Taubenberger, who have been seeking to learn where the 1918 flu virus came from and what made it so deadly. Using fragments of undamaged 1918 virus found in lung tissue of a flu victim, Taubenberger and his team set out to map the genes of the killer flu. Since the original broadcast of this program, Taubenberger's team successfully created a genetic sequencing of the 1918 virus, resurrected the virus itself to study its effects on lung tissue and announced a striking similarity between the 1918 virus and the H5N1 avian flu virus. The updated episode includes new material and interviews with Taubenberger that reflect new findings.