Evolution of 1918 Flu Virus Traced from Century-Old Samples

Amazing stuff! Forensic analysis after more than 100 years. 

"... Research published today (May 10) in Nature Communications fills in some of the gaps in that body of knowledge: researchers managed to extract viral genomes from tissue samples of people who caught the 1918 pandemic flu in different years to show how the virus mutated over time to adapt to the human immune system. They conclude that the virus may have evolved into the pathogen that circulated as a seasonal flu after the pandemic ended. ...
Working with 13 formalin-fixed lung samples that were collected from people who died in Berlin between 1913 and 1920 of the flu or other bronchial diseases, Wolff, Calvignac-Spencer, and their colleagues only managed to extract one complete and two partial genomes. But these included the first-ever genomes of the virus from before the pandemic’s initial 1918 peak ...
the idea that the seasonal H1N1 virus that followed the 1918 pandemic stemmed from the pandemic virus is well established, but the underlying mechanism was less clear. ..."

From the abstract:

"The 1918 influenza pandemic was the deadliest respiratory pandemic of the 20th century and determined the genomic make-up of subsequent human influenza A viruses (IAV). Here, we analyze both the first 1918 IAV genomes from Europe and the first from samples prior to the autumn peak. 1918 IAV genomic diversity is consistent with a combination of local transmission and long-distance dispersal events. Comparison of genomes before and during the pandemic peak shows variation at two sites in the nucleoprotein gene associated with resistance to host antiviral response, pointing at a possible adaptation of 1918 IAV to humans. Finally, local molecular clock modeling suggests a pure pandemic descent of seasonal H1N1 IAV as an alternative to the hypothesis of origination through an intrasubtype reassortment."

Evolution of 1918 Flu Virus Traced from Century-Old Samples | The Scientist Magazine® The work reveals that the pandemic flu was likely the direct predecessor of the seasonal H1N1 flu that circulated for decades.

Archival influenza virus genomes from Europe reveal genomic variability during the 1918 pandemic (open access)