An agent of the “Contact Tracing” platform in Toulouse who calls a patient to find his contact cases. – H. Menal – 20 Minutes
- For several months, Health Insurance has been responsible for contact tracing, which consists, once a person has tested positive, in contacting all those they may have infected after their contamination.
- On the contrary, retrotracing, practiced in Japan in particular, consists of tracing the chains of contamination, and would be more effective in identifying clusters and super-contaminators as early as possible.
- Can this method be deployed effectively in France? An experiment is being carried out in two departments by the Health Insurance to find out more.
” Test. Trace. Isolate ”. Or rather now: “Test. To alert. Protect “. The government’s slogan has evolved, but the credo remains the same: mass screening and tracing to break the chains of coronavirus contamination. In France, health insurance agents engage in prospective tracing. It consists in identifying the contact cases of a person tested positive for Covid-19 to know, from the time of his contamination, to whom he is likely to have transmitted the coronavirus. What if we did the opposite? Going back to the source of the contamination? This is the concept of retrotracing, or Japanese-style tracing.
This new method of tracing is being tested in Côte d’Or and Loire-Atlantique, the Health Insurance announced on Wednesday, while France is facing an explosion of the epidemic and the Head of State should announce a new screw tightening. How does it work? And can it be applied effectively in France?
What is retrotracing?
“With retrotracing, we go back and ask positive people about the very moment of their contamination. We ask them if they have an idea of where they may have been infected, during a professional meal without a mask or a meeting without respecting barrier gestures, ”detailed Thomas Fatôme, General Manager of the Fund. national health insurance (CNAM), in an interview on Sunday Parisian. With Japanese-style tracing, rather than unwinding the thread of the contamination chain, the agents will therefore go back to the source and search for all the people who participated in the event during which the person may have become infected.
“We then ask all those who participated to isolate themselves and be tested,” confirmed Thomas Fatôme. Either tracing at the sources of contamination, hence the term retrotracing, or retrospective tracing. “The retrotracing therefore consists, for the Health Insurance, in questioning the patient zero on the place where he could have contracted the Covid-19, on the person who could have contaminated it and the co-exposed people”, explains the Health Insurance. Then “to contact the person or people present at the suspected place, to ask them to be tested and to isolate themselves.” This makes it possible to break the chains of contamination upstream, in addition to the downstream already covered by contact tracing ”.
Is this method more efficient?
“According to the ComCor study conducted by the Institut Pasteur, 44% of infected people know the source person who infected them. These people are covered by the contact tracing currently practiced and called to be tested and to isolate themselves ”, explains the Health insurance. But the advantage of the Japanese method is that it “makes it possible to go further: it is estimated that 10 to 20% of zero patients contacted are able to determine an event or a circumstance that could be the result. origin of their contamination ”, continues the Health Insurance.
And 10 to 20% of cases alone are responsible for 80% of contamination, according to a study recently published in the leading scientific journal Nature. This finding has prompted Japan and other Asian countries to opt for this tracing method to move in two directions: identify super-contaminating people who can sometimes infect dozens of people, and therefore bring to light more effectively clusters, while identifying the places where we are most contaminated.
A method all the more interesting as prospective tracing is regularly accused of ineffectiveness. ” The strategy [du tracing classique] is not in phase with the reality of the circulation of the virus, indicated to 20 minutes epidemiologist Catherine Hill, because she says nothing about the transmission of the virus ”. Because in practice, between the moment of contamination, the onset of symptoms and screening, it can take up to “ten days, according to the epidemiologist. We realize that patients are contagious when they are no longer. It’s too late to prevent them from contaminating around them. And at that point, we look for their contacts who have themselves already infected around them. This is why we have never controlled the virus ”. Without forgetting the asymptomatic patients who pass through the cracks of the net.
Can this Japanese-style tracing be practiced in France with a high circulation of Covid-19?
For the time being, retrotracing is only tested in two departments, the Côte d’Or and the Loire-Atlantique. Launched last Thursday, the experiment will continue until the end of April. Why these two departments? Because these are territories where the circulation of the coronavirus is relatively low.
“This technique requires that the circulation of the virus is not too important”, explained Thomas Fâtome to the Parisian. While classic tracing requires already significant human resources, the Japanese version requires even more agents. Logistics impossible to set up in territories where the circulation of the virus is particularly active, but which could be deployed if the results of the experiment are satisfactory, when the number of daily contaminations will have dropped drastically.