Covid-19: what is the reverse tracing method that would identify sources of contamination?



The contact case tracing strategy (“contact tracing “), put in place since the deconfinement to break the chains of transmission of Covid-19, would it be the best strategy to adopt? In any case, this method could evolve if we compare to other countries which practice reverse tracing.

Example in Japan. There, preventing contact cases is necessary, but often it concerns relatives who are already aware of the situation, such as the patient’s spouse, his children, his parents, his colleagues … going up the thread, by finding out who it was contaminated, we can go back to these famous “clusters” or hotbeds of cases, because some researchers believe that many contaminations are the involuntary work of those who are nicknamed the ” super contaminators ”. We remember, at the start of the epidemic in France, in February, a man of British nationality, who had stayed in the chalet in Contamines-Montjoie (Haute-Savoie), had infected eleven people.

This reverse tracing method would also make it possible to identify areas where we are contaminated. Epidemiologists have identified slaughterhouses, choirs, but doubt still remains about the spread of the virus in public transport, in bars or in restaurants.

Reverse tracing has already been used with us. Last February in the Oise, the health authorities sought to determine the person or people at the origin of the contamination of two positive coronavirus cases who had not traveled to a risk area. But why are we not doing it anymore? Because finding who has infected a person is extremely long and tedious. Was it in the metro, in the canteen, at the hairdresser? Often we do not know. Moreover, in the Oise, the identity of patient zero has not been completely decided. This method of reverse tracing is like a police investigation: painstaking work. In the midst of an epidemic, it is not certain that epidemiologists have the time necessary for this.

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