Positive mid-August, again at the beginning of September, and… negative in the meantime.
The "case" Steve Mandanda, forced to leave the group of the French team after being diagnosed positive for Covid-19 Thursday evening, asks many questions.
The goalkeeper was tested twice, Wednesday and Thursday, almost three weeks after a first positive result, on August 16 in Marseille.
Except that it had been negative in the meantime, on August 23 and then on August 27, we say among the Blues.
Without symptoms, he even kept OM's goal for the first game of the season, against Brest, on August 30.
Poor sample quality
First hypothesis: the two “normal” tests carried out at the end of August could actually be… “false negatives”.
This "can occur when the virus is still present in the body but not enough for the individual to test positive", indicates the virologist Yves Gaudin, of the Institute of Integrative Biology of the Cell (I2BC) of Paris- Saclay.
The infectious disease specialist Benjamin David estimates for his part that "the proportion of false negatives is at least 30%".
One of the reasons would be the quality of the screening.
“We expanded the list of people authorized to perform the clinical examination.
Obviously, when you have young people and students who can do it, you do not necessarily have the same quality of sample obtained by going far enough [into the nose] and turning the swab well ”, supports the doctor of the Raymond-Poincaré hospital, in Garches (Hauts-de-Seine).
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The second hypothesis to explain the Mandanda "case" is that of a "false positive" this week.
Because doctors and scientists consider it entirely possible that traces of the virus are detected in the body of an infected individual several weeks or even a few months after infection.
“This is called chronic carriage.
At first, an individual has a lot of viruses.
And after a while, he loathes a lot less but enough to be tested positive by PCR ”, explained mid-August Jean-Daniel Lelièvre, the head of the infectious diseases department at the Henri-Mondor hospital in Créteil. (Val de Marne).
In an opinion of July 27, the Scientific Council already pointed out the existence of such cases of "negativation of the PCR then reappearance of a weak positive signal, in the absence of clinical signs".
"This situation reflects the possibility of viral RNA to remain non-infectious in cells at very low concentrations," the scientists wrote, adding that this "is only a reflection of non-infectious persistence of 'Viral RNA, and should not be considered as reinfection or viral persistence ”.
Level of contagiousness linked to viral load
A PCR test can therefore give a positive result, without the person being very contagious.
Because the more the virus is important, the more the person is likely to infect others.
A low viral load is "often the reflection of a low or zero quantity of virus signaling that the tested person does not present a risk, in particular if this detection is done in a context of measurable rise of antibodies", was he still indicated in the opinion of the Scientific Council.
"Clearly, we know that there is a correlation between the viral load and the level of contagiousness", supports the virologist Yves Gaudin.
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"20 days before a first test, as there is no reason that he has already been re-infected, Steve Mandanda is probably no longer contagious", adds Benjamin Davido.
The problem is that the PCR test carried out in France is binary.
It simply indicates whether or not virus is detected in the back of the nose.
“To completely rule out the hypothesis that Mandanda could infect other people, it would be necessary to test for contagiousness with a viral culture.
But this is not done in an hour, ”adds the infectious disease specialist, who works in particular with the French Tennis Federation on the organization of Roland-Garros.
The New York Times reports, after close examination of three groups by scientists, that "up to 90% of people who tested positive carried virtually no virus".
" Precautionary principle "
In "respect of the rules" and by "principle of precaution", Mandanda was therefore forced to leave the French group, we assumed at the Blues Thursday evening.
What anger the leaders of OM.
There was no negligence in Marseille, they hammer home.
According to them, the doctors of the France team made a mistake: they would not have communicated the correct documents to UEFA.
And if they had specified that Steve Mandanda had already been ill, then cured, UEFA would have known that the PCR test carried out this week should not be taken into account, the club said.
And the OM to recall that the Professional Football League also recommends, in its protocol, not to do tests on the recovery of a player with Covid-19.