Every day, Le Parisien takes action to answer your questions about the coronavirus. Today we are interested in this question from a reader: "Was the coronavirus present in France in early January? "
This question was asked to us with reference to several facts, while the first cases were officially detected on January 24 in France. The first is that the World Health Organization (WHO) dates the appearance of the first symptoms of the virus in China to December 8, which, logically, would suggest the possibility of contamination in the following weeks in countries with a lot of trade with Asia, such as France.
Similar symptoms before official cases
The second is linked to numerous testimonies from people suffering from Covid-19 symptoms before the official detection of the first cases in France. Contacted by the Parisian, several of them describe having been diagnosed with flu or colds with unusual symptoms, such as temporary loss of taste or smell, diarrhea, strong coughs that last, very tired, and / or difficulty breathing. However, they have so far been unable to carry out a test confirming or denying their contamination.
At this stage of the epidemic, not all specialists hold the same discourse on the date of actual appearance in France. "A presence in early January is very highly likely, even perhaps before," replies for example Jean-François Guégan, research director at INRA-CIRAD and specialist in the ecology of infectious and parasitic diseases. And to insist: "Will research prove it?" Very probably. As with each epidemic, cross-analyzes between molecular biology and dynamic transmission will be carried out, "he continues, adding that since the incubation period of the virus is 4 to 15 days, it could have been present before symptoms of the first cases reported.
Too few cases identified for a start in January?
For his part, Samuel Alizon, director of research at the CNRS, also a specialist in the ecology and evolution of infectious diseases, favors the thesis of a spread from February. "The viral genomes suggest, with a fairly large margin of error, the arrival of the first cases from February and an epidemic that grew from there," he summarizes, based on a long series calculations.
“If we consider a hidden circulation of the epidemic in January, the figures make little sense. You then have 70 days (of circulation of the virus, NDLR) or 28 doublings (according to a calculation providing for a doubling of cases every 2.5 days, NDLR) and a size on March 11 of… 268 million infections. If the epidemic had circulated in January, it would have had to be done without transmission, which does not really make sense, "he says.
The two specialists interviewed on this question agree on one point: it will be necessary to wait for the arrival of new data to have a formal answer on the subject. And it will take time.
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