A study by French scientists indicated that the coronavirus outbreak in France was not caused by cases imported from China, but from a locally circulating strain of unknown origin.
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The COVID-19 pandemic has infected more than 128,000 people in France and caused more than 23,000 deaths. In order to find out about the initial introduction and spread of the coronavirus in France, scientists in the Pasteur Institute, a research center of infectious diseases in Paris, conducted a phylogenetic analysis by sequencing 97 genomes from samples in France and comparing them with the 338 sequences from GISAID database.
The findings were shown in their pre-printed paper “Introductions and early spread of SARS-CoV-2 in France” published on biorxiv.org on April 24. It pointed out that the dominant strain of the outbreak in the country was linked to the genetic group clade G, which was not from China or Italy. The early introductions “do not appear to have resulted in local transmission” due to the quarantine imposed on the initial imported cases. By mentioning this, the paper highlighted the efficacy of the measures taken by France to contain the coronavirus. Therefore, the COVID-19 outbreak in France did not come directly from China.
The study found that the earliest representative of clade G (HF1463) had no history of travel or contact with returning travelers, so the scientists infer that the virus had been circulating undetected in France and other European countries for a long time before the outbreak in February, since there are a large proportion of mild or asymptomatic diseases, which were difficult to detect at that time.
The paper also pointed out the inadequacy of the present study, adding that more thorough sampling will be needed to trace the source of the virus in France. However, the paper does have its great contribution. “Our study sheds light on the origin and diversity of the COVID-19 outbreak in France with insights for Europe, and highlights the challenges of containment measures when a significant proportion of cases are asymptomatic,” it suggested.