A pair of lungs preserved over a century ago from a deceased Spanish flu patient has helped unravel the genetic adaptations undergone by the virus to spread across Europe during the start of the 1918 pandemic.
The Spanish flu pandemic of 1918-1920 was one of the most devastating pandemics in history, claiming some 20 to 100 million lives worldwide.
However, little is known about how the flu virus mutated and adapted throughout the pandemic.
Understanding how viruses evolved during past pandemics remains crucial for developing targeted countermeasures for the future, researchers say.
Scientists have now reconstructed the first Swiss genome of the influenza virus behind the 1918 pandemic, helping unravel how it spread across Europe during its initial waves of infections.
Researchers used an over 100-year-old virus sample taken from a formalin-fixed lung specimen in the Medical Collection of Switzerland’s University of Zurich.
The virus sample was taken from an 18-year-old patient from Zurich who died during the first wave of the pandemic in Switzerland and underwent an autopsy in July 1918.
“This is the first time we’ve had access to an influenza genome from the 1918–1920 pandemic in Switzerland. It opens up new insights into the dynamics of how the virus adapted in Europe at the start of the pandemic,” said Verena Schünemann, a co-author of the study from the University of Zurich.
Researchers compared the Swiss genome with versions previously published from Germany and North America to find that the Swiss strain already carried three key adaptations to infect and spread among humans that would persist in the virus until the end of the pandemic.
Two of these mutations seem to have made the virus more resistant to the human immune system, an important barrier against the transmission of such flu viruses originating from animals.
Another mutation of a protein in the virus’s membrane improved its ability to bind to entry point receptors in human cells, making it more resilient and infectious.
In the study, scientists used a new method with improved ability to recover ancient RNA fragments from specimens.
“Medical collections are an invaluable archive for reconstructing ancient RNA virus genomes. However, the potential of these specimens remains underused,” said Frank Rühli, another author of the study.
Researchers hope future studies using the method could lead to a better understanding of how viruses adapt to humans during a pandemic, enabling us to better anticipate and adapt to future pandemics.
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