Officially, the first case detected in France comes from China. However, geneticists claim that the Covid-19 does not come directly from the country where the epidemic is located and was already circulating freely in France in mid-January. How is this possible?
What if Covid-19 did not come directly from China? Quite officially, the first case on French territory is an 80-year-old man from the province of Hubei (China). However, he arrived in Paris on January 23, 2020. Remember that the epidemic took a long time to settle in France. On February 17, for example, the country had only 12 cases, most of which were imported.
And yet, it could well be that the Covid-19 was circulating freely from mid-January ! This hypothesis is that of researchers from the Institut Pasteur who published their study on the bioRxiv platform on April 24, 2020. According to the researchers, asymptomatic (no symptoms) or paucisymptomatic (few symptoms) people already carried the virus long before the virus. large wave of cases in March.
It should be noted that monitoring of Covid-19 began in France on January 10. About two weeks later, the first three cases imported into Europe have been detected in the country. In addition, the first strains of the virus were sequenced in France between January 23 and January 29 and all came from the Wuhan region. Then, the other strains came from people who had resided in Italy.
According to the publication of the Institut Pasteur, the study takes into account biological samples collected until March 24, 2020, namely 97 viral strains . However, it should be noted that the reconstruction of the phylogenetic tree also takes into account other genetic sequences from other international teams. Thus, the researchers were able to determine the genetic diversity of the viral strains that appeared in France (variants).
Nowadays, these variants no longer really circulate among the population. The isolation of the first cases made it possible to avoid the implantation of these variants. Moreover, it turns out that an overwhelming majority of viral genetic sequences all belong to the same set . Because of their very low genetic diversity, researchers have classified them within the "G lineage".
The Institut Pasteur has one of the earliest G lineage strains on a European scale. The latter actually dates from February 19 and concerns an infected person in the Oise department. However, this person has not traveled and has not been in contact with other people returning from a trip. For the researchers, the Covid-19 was already circulating freely and above all silently in the Oise. However, it was probably circulating in other regions at the same time, given the low diversity at the strain level. Thus, the virus was certainly introduced into France on several occasions and this around mid-January or, if necessary, at the beginning of February.
However, it should be remembered that the study remains to be verified because it is currently on bioRxiv, a pre-publication platform. In addition, these Institut Pasteur estimates may change in the future. Indeed, the researchers did not have a large number of strains and these did not sufficiently represent all the French regions. Nevertheless, the researchers estimate that 95% of the strains circulating in France currently belong to this G lineage. Thus, most cases would come from local chains of transmission and not from imported cases.
