In 1918, people started getting sick. Really sick. A new strain of influenza had arrived, and it quickly spread, becoming a global pandemic that killed millions. Researchers have now pieced together the virus’s genetic code using samples from three people who died of the flu to uncover how the virus changed during the pandemic (Nat. Commun. 2022, DOI: 10.1038/s41467-022-29614-9).
When virologist Sébastien Calvignac-Spencer of the Robert Koch Institute visited the Berlin Museum of Medical History, he was looking for historical samples he could use to test how to extract viral information from preserved tissues. When he found lung samples from 1918 in the basement, he says, it seemed like a natural place to start. He wasn’t hopeful, but he assembled a team to look for preserved viral RNA. They found some.
The researchers managed to find and read flu RNA in 3 of the 13 specimens eventually tested. Two of those samples came from young soldiers who died in Berlin, and the other came from a young woman who died in Munich.
The researchers compared their new genomes to the only other known sequences of the 1918 flu—one from a woman buried in Alaskan permafrost and the other from a soldier in New York. They found that the genetic code for the 1918 flu changed considerably over time, altering key proteins like the RNA polymerase and the nucleoprotein. The team says these mutations might explain why the virus’s behavior changed during the pandemic. The sequences also suggest that the seasonal H1N1 flu descends from the 1918 pandemic strain.