107-year-old lung used to revive deadly Spanish Flu genome: This changes history

Scientists have successfully revived the genome of the Spanish Flu that struck the world in 1918. This was thought impossible since the lung it was decoded from had been preserved in a substance that damages the RNA. The achievement was revealed in the peer-reviewed study published in the journal BMC Biology. The influenza A virus (H1N1) strain was taken from the lung of an 18-year-old man who died in the first wave of the Spanish Flu pandemic in Switzerland. Sequencing of the genome has also shown how the virus mutated rapidly in the early stages to adapt to the human body. A team of European researchers took the preserved autopsy sample from the lung tissue that had been placed in formalin. It was kept at the University of Zurich’s medical collection, and no kind of study was carried out on it for over 100 years. Dr Verena Schünemann and his team managed to sequence the genome despite the lung sample ZH1502 being kept in formalin, which causes crosslinking and damages RNA. He said in the paper that not only did their work reveal the virus’s genetic structure, but also showed that it was fast-changing in the early days of the pandemic.

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To overcome the challenge posed by formalin, Schünemann’s team developed a new ligation-based RNA sequencing protocol. This method was specifically devised to work on degraded or ancient viral RNA and helped them recover more than 98 per cent of the viral genome at high quality. It avoids the use of phenol-chloroform chemicals to be able to retain information about RNA strand orientation. They found that several mutations occurred early on in the virus, since this man died on July 15, 1918, during the first wave. This finding shows that the virus quickly turned dangerous, as opposed to previous theories that state it only mutated towards the second half of 1918. "The virus already showed signs of human-specific adaptation well before the second wave hit," the researchers wrote in the paper.

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Spanish Flu timeline changes

This changes the timeline of the virus since earlier samples sequenced came from the autumn or winter of 1918, showing dangerous viral changes. But now that the genome from the summer of the year has also been revived, it shows that the virus was becoming deadly much earlier. However, it isn't clear whether this represents co-circulating viral strains or a swift mutation sweep. The researchers compared the 1918 genome diversity with that of the 2009 H1N1 pandemic, and determined that the Spanish Fly strains had more genetic diversity in certain segments. Scientists believe there could be several more such tissues in formalin and the new methodology can be used to gain insights into diseases like tuberculosis, HIV, or pre-antibiotic bacterial infections.