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of French people infected long before the first official cases testify for the first time

They still can’t believe it. When we took a blood sample from them in November and December 2019, they had no idea that they were carriers of SARS-CoV-2, and that they would become the first French people to be infected long before the outbreak of the epidemic. . It was indeed almost a year later, in September 2020, that they learned that they had been infected. Professor Fabrice Carrat, director of the Pierre-Louis Institute for Epidemiology and Public Health (Inserm, Sorbonne University), had the idea of ​​analyzing 9,000 blood samples taken from participants in the Constances * cohort. “Since 2018, volunteers have been offered to participate in the establishment of a biobank, explains Marie Zins, the scientific director of this project. They allow samples of their blood and urine to be frozen in large nitrogen tanks for further research. With Professor Carrat, we said to ourselves that it would be interesting to find traces of the virus, that is to say the presence of antibodies between the month of November 2019 and the month of March 2020.”

All 9,000 participants’ blood samples were tested, which identified 176 positive cases. A second test, deemed reliable and more specific, then made it possible to eliminate the false positives to retain only thirteen, including ten that had been taken in November and December 2019 (see here the report of the published study February 6, 2021). Then, the people answered questionnaires which allowed to know more about the circumstances of their infection.

Among these “real” positives, there is a thirty-something who lives in Paris, whose blood test analyzed dates back to November 29, 2019. When he learned a posteriori his positivity by a letter from Inserm in September 2020, he did not Can not believe his eyes, as he tells the investigation unit of Radio France: “I knew my roommate had spent four days in Montreal, Canada in early November. A week later, he began to have very strong coughing fits. What was very striking was that I had the same thing as him, around November 8 or 10, a week before the blood sample I did for the Constances cohort.“The young man has very strong coughing fits.

“It was a very dry and very long cough, lasting 20 to 30 seconds. It felt like I was coughing up my lungs, so much so that I thought I would go see a doctor.”

A Parisian, tested positive for Covid-19 in November 2019

to franceinfo

But after a few days, the symptoms passed. He didn’t ask himself any more questions.

Another 40-year-old man we met at his home in southwestern France spent nearly two months in China with his wife. When he learned that he had been a carrier of the Covid-19 virus in early December 2019, he made the connection with the trip he had made from October 17 to December 9. “We arrived in Beijing, he explains. Then we went south, more on the west side, on the Tibet side. We went back to central China, then we went back down to Canton, Macao and then Hong Kong. And then we went back to France.“But the couple did not stop in the capital of Hubei:”At no time did we go to Wuhan. As closely as possible, we were about 400 km away ” [voir leur parcours ci-dessous].

Eight days after landing on French soil, the traveler takes a blood sample – one that will be analyzed and tested positive nine months later. Impossible to know precisely where it was contaminated. But for Professor Carrat, there is little doubt that it was in China that he contracted the virus, and therefore elsewhere than in Wuhan where he did not go, at a time when the epidemic did not. had not started: “We cannot guarantee that he did not become infected after his arrival on French territory on December 9. But it takes about 12 to 15 days for an individual to develop an antibody response detectable with our methods. This would mean that his rise in antibodies would have been much faster than that of other people who become infected. It’s unlikely. It is therefore much more likely that he was infected in Asia in November, and even in October. “

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The traveler does not remember that he and his wife had signs of illness during the trip, nor after: “We didn’t have a fever or cough, and we never needed to change our schedule for health reasons.

Several people, on the other hand, presented symptoms characteristic of Covid-19. A 32-year-old woman who lives in Brittany remembers several disturbing signs she had felt at the time, and which she had not been able to explain. “I had symptoms of sinusitis but with exceptional fatigue at the slightest effort, going up the stairs for example. It lasted several days. “Her husband was coughing a lot,”so intensely that it prevented him from sleeping“, she continues. She also had difficulty performing a test to measure her breath, during the assessment that she then took for the Constances cohort on November 18, 2019:”I was really out of breath and couldn’t pass this test. The nurse said to me: ‘You are young, it’s weird!’

Today, the young woman thinks she was infected at the hospital where she went several times a week during the month of October to treat a broken forearm that had worsened. . Another young woman presented with a symptom characteristic of SARS-CoV-2. “She lost her taste and smell, explains Professor Carrat from Inserm. She had been in contact with a family member who suffered from pneumonia of unknown origin between October and December, and she visited Spain in November.”

Other people, however, did not show any symptoms. Pascale, in her forties, whom we interviewed at her home in Villeurbanne (Rhône), tested positive on blood samples dating from November 2019. Hence her surprise when she received the results by a letter from the cohort Constances in September 2020. “I tried to remember if I hadn’t had a runny nose at the time, a cough, or a headache. But no, really, I didn’t have any symptoms.“She had not traveled overseas, so she looked to see if she had come into contact with people with unexplained symptoms.

“I questioned my entourage, the people with whom I had spent a birthday evening. I asked them if they had been positive. Absolutely not.”

Pascale, tested positive for Covid-19 in November 2019

to franceinfo

A female doctor based in Lyon and tested positive in mid-January 2020, tells us that she also does not remember having been sick. She thinks she was infected by several patients suffering from sinusitis and bronchitis which had lasted abnormally.

In Angoulême, a man who tested positive in mid-November 2019 and also asymptomatic, evokes packaging of products from China that he handled at the time at his work, without being able to establish a proven link with his contamination.

All 9,000 blood samples from participants in the Constances cohort were tested, which identified 176 positive cases, including ten that were taken in November and December 2019. (NICOLAS DEWIT / RADIOFRANCE)

These testimonies call for several questions:

1 – Was the virus circulating in China other than Wuhan before the start of the epidemic? It is possible, since the French traveler who was infected in this country did not go to Wuhan. However, it may have been contaminated, for example, by a person who came from Wuhan. Nevertheless, Professor Carrat of Inserm “don’t think everything was born in Wuhan. ”

“What was born in Wuhan is the virus we know in France and which gave rise to this pandemic. That does not mean that the virus was not there before. It was circulating.”

Professor Carrat (Inserm)

to franceinfo

2 – If the virus was present in other regions in October or November 2019, how to explain that the epidemic started in Wuhan? Fabrice Carrat hypothesizes that if the virus circulated in other places in China, it is in Wuhan that it would have mutated to become more contagious: “The virus that infected the French traveling couple in China may have been a variant that was less well transmitted than the one that arrived in Wuhan on December 8. And above all, it is undoubtedly a variant which gave a little less serious forms“, he explains. But for the professor, it was indeed the same virus:”It was not a seasonal coronavirus like the ones we are used to seeing in winter epidemics. It really was SARS-CoV-2, but maybe it was a precursor variant to the one that gave the global epidemic.”

3 – If the virus arrived as early as November or October, why did the epidemic not start earlier? For Florence Débarre, who does modeling in evolutionary biology at the CNRS, the cases were perhaps not numerous enough to start an epidemic. “If the cases revealed by the work of Professor Carrat are true positives, it is possible that there were a few cases, but that it stopped by the effect of chance. It has been said that one person affects three on average. But that’s an average. Some do not infect anyone, while others infect a lot. So the probability of a first case giving rise to an epidemic is relatively low.

4 – Finally, if the virus was circulating in France several months before the start of the pandemic, is it possible that this virus did not come from China? “The most likely hypothesis is that the birthplace of SARS-CoV-2 is China, explains Professor Jean-Claude Desenclos, epidemiologist and former scientific director at Public Health France. The closest SARS-CoV-2 ancestor was already identified in 2013 in China. So, all this makes a bundle of arguments which makes this hypothesis the most likely.”

* The Constances cohort is the largest epidemiological cohort currently monitored in France with 220,000 individuals monitored over the long term. It was launched in 2012 and financed by the State’s Investments for the Future program. The objective is to understand what are the factors that increase the risk of disease of the participants – all volunteers – such as the environment or work.

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