Scientists from the universities of Basel and Zurich deciphered the viral genome of the 1918-1920 influenza pandemic in Switzerland using a historic specimen. According to the study, this virus had key adaptations to the human being from the start of the deadliest influenza pandemic in the world.
One of the most devastating pandemies in history was the so-called “Spanish” flu of 1918-1920, which made between 20 and 100 million deaths worldwide. Until now, science has known little about the way in which the influenza virus of the time has evolved following changes during the pandemic.
>> Lire : How the Spanish flu could have left up to 100 million dead
An international research team, led by the paleogenetician Verena Schünemann, of the University of Basel, managed to reconstruct the first Swiss viral genome of this pandemic.
The virus, more than 100 years old, comes from a damp preparation fixed in the formalum of the medical collection of the University of Zurich (UZH). The carrier was an 18 -year -old patient who died in Zurich: his autopsy was carried out in July 1918, at the start of the first wave of propagation of the pandemic in Switzerland.
Three key adaptations
“For the first time, we have a genome from the 1918-1920 influenza pandemic from Switzerland, which allows us to have a new overview of the dynamics by which the virus has adapted to the start of the pandemic in Europe”, explains the Schünemann proffess, quoted in the press release.
By comparing this genome with others already published in Germany and North America, scientists have been able to show that the Swiss viral genome already had three key adaptations to humans, which were preserved in viral populations until the end of the pandemic.
![Phylogeny on a temporal scale of HA sequences of IAV pandemic viruses from 1918 and 1919. The American sequences are in gray, the European sequences published in green and the new ZH1502 sequence in red. The support values are only given for branches with a posterior probability of more than 80%. [BMC Biology - C. Urban, V.J. Schuenemann & al.]](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///ywAAAAAAQABAAACAUwAOw== "Phylogeny on a temporal scale of HA sequences of IAV pandemic viruses from 1918 and 1919. The American sequences are in gray, the European sequences published in green and the new ZH1502 sequence in red. The support values are only given for branches with a posterior probability of more than 80%. [BMC Biology - C. Urban, V.J. Schuenemann & al.]")
Two of these mutations made the virus more resistant to an antiviral component of the human immune system, a normally important barrier against zoonoses such as avian flu for example.
>> Consult: Podcast: Are the viruses useful?
The third adaptation concerns a protein of the viral membrane which, thanks to genetic mutation, can better bind to the receptors of human cells. The virus has thus become both more resistant and more infectious, according to these works Published in the BMC Biology review.
RNA viruses, like those of flu, decomposing quickly, scientists have developed a new method of sequencing historical RNA fragments. This technique should allow the future to rebuild other former viral genomes and better understand the progress of pandemics.
>> Lire : From the plague to the Spanish flu, what the story tells us about the end of the pandemics
ats/sjaq
