Johan Hultin, a medical researcher whose work on the 1918 influenza virus led to breakthroughs in viral mapping, has died at age 97, The New York Times reports. Hultin’s discovery in the 1950s of a frozen victim of the 1918 flu pandemic, in Alaska, gave scientists the chance to map the virus’s genetic material.

Johan Hultin’s discovery was crucial to finding the genetic sequence of the virus, allowing researchers to examine what made it so lethal and how to recognize it if it came again. The virus, which was 25 times more deadly than ordinary flu viruses, killed tens of millions of people and infected 28 percent of Americans, dropping the average life span in the United States by 12 years.

Johan Hultin’s quest to find victims of the 1918 flu was sparked in 1950 by an offhand remark over lunch with a University of Iowa microbiologist, William Hale. Dr. Hale mentioned that there was just one way to figure out what caused the 1918 pandemic: finding victims buried in permafrost and isolating the virus from lungs that might be still frozen and preserved.

Johan Hultin, a medical student in Sweden who was spending six months at the university, immediately realized that he was uniquely positioned to do just that. The previous summer, he and his first wife, Gunvor, spent weeks assisting a German paleontologist, Otto Geist, on a dig in Alaska. Dr. Geist could help him find villages in areas of permafrost that also had good records of deaths from the 1918 flu.

Get the full story at nytimes.com.