Kept in formalin, deciphered by genetics, early 20th-century European lung tissue yields new insights into Spanish flu, from which one of the seasonal flu viruses may have originated directly, according to a study published in the journal Nature.
The most devastating respiratory pandemic of the 20th century, the so-called Spanish flu of 1918-1919-a misleading term because this pandemic was far from concentrated in Spain-killed 50 to 100 million people.
Its viral origin was not confirmed until the 1930s. Subsequent research identified the culprit: an influenza A virus of the H1N1 subtype.
But there are still mysteries about the Spanish flu. Geneticists have been trying to disperse them for twenty years, but their work is limited to the low number of victim specimens to be examined.
After about fifteen fruitless steps, Sébastien Calvignac-Spencer, a viral evolution specialist at the Robert Koch Institute (Germany), said he and his colleagues were super lucky. They had access to 13 lung samples stored in formalin in museums in Berlin and Vienna, from 1901 to 1931, including 6 from 1918-1919.
And they found fragments of RNA from the Spanish flu virus in three samples from 1918.
These researchers were able to sequence large portions of the virus that infected two people, but an entire genome also in the third case. data, there are only sequences from 18 specimens worldwide, two complete genomes, in the United Statesat there is no genetic information in the early stages of the pandemicunderlined Sébastien Calvignac-Spencer at a press briefing.
The Spanish flu, in fact, experienced three big waves. The second and third were particularly deadly, more so than the first formed in the spring of 1918.
In particular, their work saw genomic variations during the pandemic and its course around the world through round trips favored by the transfers of soldiers at the end of the First World War.
From the earliest days of the Spanish flu, a gene in the virus appears to have evolved to counteract the human immune response.
Most of all, these new tests are compatible with the scenario of a pure pandemic source of seasonal flu virusesa direct parent, according to the study.
It defeats other hypotheses on the emergence of seasonal flu, especially the idea – known as the reassortment – that current viruses will generate several fragments from different ancestors.
On the other hand, it is difficult to describe how the flu pandemic of 1918 gradually became a seasonal virus, due to lack of data especially in the 1920s, explained Thorsten Wolff, virologist at the Robert Koch Institute.
Can this research provide some key to the evolution of COVID?
If we cannot compare these two pandemics, given different viruses, different conditions of propagation, different organized and connected peoplesome similarities may exist, according to Sébastien Calvignac-Spencer.
For example, the flu in 1918 had some waves like COVID, but unlike the current pandemic, where the waves are associated with new variants, this is probably not the case for the pandemic in 1918 according to our analysis. study.he says.
The study published in Nature however, there is a limit, to its very small sample sizeidentify its authors, emphasizing that their results remain foreplay.
Additional genomes from surrounding samples during the pandemic, as well as phenotypic characterization of some 1918 viruses in vitro at livewill no doubt allow a more robust evaluationThey said.
It remains to find newly preserved pathological specimens.
Source: Radio-Canada
