Covid-19: should all French people be tested to stop the epidemic?

SCREENING – “Test, test, test”, already recommended the WHO (World Health Organization) in the spring, in the middle of the first wave of Covid-19. As the authorities encourage screening, with a total of 18,935,092 tests carried out so far according to Public Health France, several doctors and politicians advocate massive screening of the population.

We must “drastically reduce the number carriers of the virus by identifying all people asymptomatic ”, wrote in particular professors Philippe Amouyel, Luc Dauchet and Emmanuel Hirsch in a column published in Sunday Newspaper on November 15th. Screening 67 million people would make up for the lack of data on the epidemic with a view to deconfinement, said Philippe Amouyel, on France Inter the next day.

Laurent Wauquiez, president LR of Auvergne-Rhône Alpes, meanwhile announced that he wanted to organize a massive campaign of free tests for the 8 million inhabitants of his region, one of the most affected by the coronavirus. The idea is attractive, but is not unanimous in France, as the response of the Minister of Health showed on BFM TV. “What is important is not to test people, it is to be sure that once tested, we are able to protect them to avoid contamination,” said Olivier Véran.

The defenders of mass screening, however, have a strong argument to make: several states have successfully carried out this large-scale operation. The city of Wuhan, the first epicenter of the epidemic in China, notably carried out a massive screening of its 11 million inhabitants last winter, until it eradicated the coronavirus. Hong Kong also conducted a massive screening in early September with 1.8 million people tested out of the 7.5 million inhabitants of the island. Beijing, or Qingdao, in China, have also succeeded in containing the epidemic by testing, without going as far as general containment of the population.

Do you know the “pooling” strategy?

These regions have opted for the “pooling” strategy, which consists in testing not each sample taken, but a mixture of several of them. When a test is positive in the batch, all samples are tested one by one to isolate the positive case.

In Europe, several countries have embarked on screening campaigns using antigenic tests. Like Slovakia, which has a little over 5 million inhabitants and which offered its population in early November to benefit from a rapid antigenic test, twice, a week apart. Two thirds of the population responded to this proposal.

Pooling or antigenic tests … should one of these techniques be applied in France to test the 67 million inhabitants? Jean-François Rupprecht, researcher at CNRS and contributor to the Adioscorona association, who militates for a massive screening of the population considers that the technique of “pooling” would be the most effective. “If we applied it in France, we could reduce the circulation of the virus to 5,000 cases per day, approximately, as Emmanuel Macron wished during his speech on October 28. The method has shown its effectiveness in New York universities (400,000 students), which have succeeded in drastically reducing the circulation of the virus thanks to screening by pooling ”, he explained to HuffPost.

However, the High Council of Public Health opposed it in a notice from May, arguing that “the false negative results” would be too important. In addition, Daniel Dunia, CNRS researcher at the Toulouse Purpan physiopathology center (CPTP) judged from the HuffPost this “useless” technique: “We are at a rate of circulation of the virus that is much too high for the virus to be effective. This would mean that all the “lots” would come back positive since many French people are infected. ”

In addition to pooling, several doctors are calling for the use of antigenic tests to screen the population in France. The sample taken from the nose using a swab has the advantage of being quick since the result is 30 minutes. But here too, the risk of false negatives is high. According to the High Authority for Health, the test is 80% reliable. “A negative test will reassure patients who are in reality infected and who will infect other people,” explained Franck Perez, CNRS researcher and director of the cancer cell biology laboratory. Your viral load peaks about four days after the onset of symptoms. All infected patients tested before this peak could therefore fall through the cracks.

A very high logistical cost

Not to mention the very significant logistical cost that such an operation would require, as Daniel Dunia explains: “Antigenic tests involve a medical act (even if they are sometimes carried out in pharmacies, editor’s note). Someone would have to be trained to perform the test, which I think is hard to imagine nationally. Hospitals are already on, or can we find them? And we don’t have enough machines for an operation of this magnitude, nor enough tests ”. In this respect, the example of Slovakia is eloquent: the country which wanted to carry out the operation twice only did so once.

Jacqueline Marvel, an immunologist specializing in tests against Covid-19, goes further: for her, massive test campaigns would have no interest in the fight against Covid-19. “This would slow down the epidemic before it starts again. But we are already getting there with containment and current health measures, so what is the point of massive screening? ” she asked the HuffPost.

Thus, faced with the limits presented by massive screening, several researchers recommend instead to focus on high places of contamination, or on regions in particular, as what Laurent Wauquiez wants to implement in Auvergne Rhône Alpes. “It’s a very good idea to do it at the regional level,” Daniel Dunia suggests. Concentrating forces on a particular region is far more achievable and will inevitably have an impact at the national level. You have to find the virus where it circulates the most, and monitor people at risk by carrying out screening campaigns in nursing homes, for example. ”

This is what the Scientific Council proposed, as summarized by Jean-François Delfraissy. in an interview with World this Friday November 20. it is preferable to conduct an experiment in one or two large French cities, to see what can be expected ”.

See also on HuffPost: To screen for the coronavirus, China says it has developed “the fastest machine in the world”

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