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

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

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

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

In Auvergne-Rhône-Alpes we will put our inhabitants to the test before Christmas.
2 million tests already ordered, 1,000 screening centers employed. Our goal: to stop the transmission of the virus and protect our seniors during the holidays. pic.twitter.com/e4HmYp4CW9

– Laurent Wauquiez (@laurentwauquiez) November 16, 2020

Advocates of mass screening, however, have a strong argument to make: several states have successfully completed this large-scale operation. The city of Wuhan, the first epicenter of the epidemic in China, in particular carried out a massive screening of its 11 million inhabitants last winter, until the coronavirus was eradicated. Hong Kong also conducted a mass screening in early September with 1.8 million people tested on the island’s 7.5 million inhabitants. Even Beijing, or Qingdao, in China, managed to contain the epidemic by experimenting, without reaching the general containment of the population.

Do you know the “pooling” strategy?

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

In Europe, several countries have undertaken screening campaigns using antigen tests. Like Slovakia, which has just over 5 million inhabitants and which at the beginning of November offered its population the benefit of a quick antigen test, twice a week apart. Two thirds of the population responded to this proposal.

Pooling or antigen tests … should one of these techniques be applied in France to test the 67 million inhabitants? Jean-François Rupprecht, CNRS researcher and collaborator of the Adioscorona association, which fights for a massive screening of the population, believes that the “pooling” technique 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 28th. The method has proven its effectiveness in New York universities (400,000 students), which have managed to drastically reduce the circulation of the virus thanks to pooling screening “, he explained to HuffPost.

However, the High Council of Public Health objected in an opinion dating back to May, arguing that “results rendered false negatives” would be too important. Furthermore, Daniel Dunia, CNRS researcher at the Pathophysiology Center (CPTP) of Toulouse Purpan, judged with the HuffPost this “useless” technique: “We are at a virus circulation rate that is too high for the virus to be effective. This would mean that all the “batches” would come back positive as many French are infected “.

In addition to pooling, several doctors are calling for the use of antigen tests for population screening in France. The sample taken from the nose using a swab has the advantage of being fast as the result is 30 minutes. But here too the risk of false negatives is high. According to the Haute Autorité de Santé, the test is 80% reliable. “A negative test will reassure patients that they are actually infected and that they will infect other people,” said Franck Perez, CNRS researcher and director of the cancer cell biology laboratory. The peak viral load is approximately four days after the onset of symptoms. All infected patients tested before this peak could then fall through the cracks.

A very high logistic cost

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

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

Thus, faced with the limitations presented by massive screening, several researchers recommend instead focusing on highly contaminated places, or regions in particular, such as the one that Laurent Wauquiez wants to implement in Auvergne Rhône Alpes. “It’s a great idea to do it regionally,” suggests Daniel Dunia. Focusing forces on a particular region is much more achievable and will inevitably have a national impact. You need 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 also what the Scientific Council proposed, as summarized by Jean-François Delfraissy in an interview with World this Friday 20 November. it is preferable to conduct an experiment in one or two large French cities, to see what can be expected ”.

See also on HuffPost: For coronavirus screening, China claims to have developed “the fastest car in the world”