Swiss researchers decode ancient “influenza virus” genome from preserved pandemic victim

Scientists have decoded the genome of the deadly 1918 influenza virus from preserved tissue of a Swiss patient, offering new insights into how the virus adapted to humans and triggered one of the deadliest pandemics in modern history. The pandemic killed an estimated 20 to 100 million people globally. Researchers say their work could help prepare for future pandemics by improving models of how viruses evolve and spread in human populations.

The breakthrough was led by researchers from the University of Zurich and the University of Basel, using a 107-year-old preserved lung specimen from an 18-year-old male patient in Zurich who died in July 1918, during the first wave of the Spanish flu in Switzerland.

"This is the first time we've had access to an influenza genome from the 1918–1920 pandemic in Switzerland," said lead researcher Verena Schünemann, a paleogeneticist at the University of Basel. “It opens up new insights into the dynamics of how the virus adapted in Europe at the start of the pandemic.”


By comparing the Swiss strain to genomes previously reconstructed in Germany and North America, the team found that the virus already carried three key adaptations to human hosts at the very start of the outbreak. Two mutations helped it resist a human immune system component that normally blocks avian-like flu viruses, while a third mutation enhanced the virus’s ability to bind to human cell receptors, making it more infectious.

These findings suggest that the 1918 virus had adapted to humans early, allowing it to spread rapidly across populations. One of the biggest challenges was recovering the virus’s fragile RNA, which degrades far more quickly than DNA. To overcome this, the team developed a new method for extracting ancient RNA from formalin-fixed tissue, a technique that could now be used to study other historical viral outbreaks.

“Ancient RNA is only preserved over long periods under very specific conditions,” said Christian Urban, first author of the study. “That’s why we developed a new method to improve our ability to recover these fragments.”

The study also highlights the untapped potential of medical archives. “Medical collections are an invaluable archive for reconstructing ancient RNA virus genomes,” said Frank Rühli, co-author and head of UZH’s Institute of Evolutionary Medicine.