Not one, not two, but three infections with SARS-CoV-2.
This mishap would have happened to a 19-year-old near Tarbes (Hautes-Pyrénées), reports France 3 on Wednesday, based on a first article published by La Semaine des Pyrénées.
But are these really "re-infections", as the title suggests?
In reality, nothing allows us to say so.
“It sounds very unusual, but three positive PCRs is not enough to tell if it is one, two or three infections.
The only way to prove it would be to sequencing the samples in order to compare the strains with each other, ”the infectious disease specialist Benjamin Davido immediately replies.
Last October, the Centers for Disease Control and Prevention (CDC, the major US health agency) listed a long series of criteria for scientifically establishing reinfection.
We take stock.
What we know about this story
Our colleagues report that the young man would have had three positive PCR tests in June 2020, in October of the same year, then in recent days, at the end of May 2021. He would have had very few or no symptoms the first two times, but he said today "not in great shape" and "not in a state to testify" ‚according to one of his relatives.
What the science says about reinfection cases
Cases of reinfection have been documented in the scientific literature.
Before the arrival of the famous variants, several studies estimated this risk between 0 and 0.2%, reports Vidal, specifying that these figures were to be taken with great caution.
"Out of 10 or 15 million people infected in France, there may have been a few thousand infected twice, so with reinfection", corroborates virologist Yves Gaudin.
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In other cases, a person may have been positive twice within a few months of each other without actually being re-infected in the meantime, but simply because RNA from the virus was detected during the PCR test. “The virus is hardly active in the body anymore, but you have kept a little. If the PCR is very sensitive, it can match, ”says Yves Gaudin. A high PCR cycle number corresponds to a low amount of viral RNA detected. “We had positive cases 64 days after symptoms ended and I'm sure people are keeping the virus for longer, latently. It does exist, ”adds Stéphane Korsia-Meffre, medical editor for Vidal. In this case, the person is generally not (or very little) contagious.
Following this logic, it is even possible to be positive, negative, then positive again.
"The late recovery of low positivity is only the reflection of a non-infectious persistence of viral RNA, and should not be considered as a reinfection or a viral persistence", indicated in July 2020 the scientific council.
All this could explain why the young person in the South-West was positive in June 2020 and then four months later.
The few symptoms experienced in the fall could have been due to another virus, not SARS-CoV-2.
In this case, there would therefore have been only one reinfection, in recent days.
What changes the arrival of variants
This hypothesis seems all the more possible since the young person had, this time, many symptoms. However, the arrival of the variants at the very end of last year increased the risk of being re-infected. Those called “Brazilian”, “South African” or one of the derivatives of that called “British” carry the E484K mutation, which reduces the effectiveness of the immunity acquired by a previous infection or by vaccination. “They can cause re-infections in people who have already contracted Covid-19,” said Olivier Véran in early February.
Nevertheless, several elements "suggest that the substitution at position 484 would not be sufficient on its own to induce a significant immune escape (post-infection and / or post-vaccination)", note Public Health France and the National Reference Center for Viruses. infectious patients in their last detailed analysis.
Read also Covid-19 reinfections: do the variants call into question immunity?
The risk would be particularly high with the South African variant. According to a study conducted in South Africa, the risk of reinfection after contamination with the original virus is around 5%, reports Vidal. On February 10, a publication in the journal Clinical Infectious Diseases reported the case of a seriously ill patient in France after being infected with this variant, "a few months after a first infection with SARS-CoV-2".
Anyway, all our interlocutors agree in saying that "the vast majority of people are protected after an infection", in the words of Jean-Daniel Lelièvre, head of the infectious diseases department at Henri hospital. Mondor. "Here [for the young person from Tarbes, Editor's note], we will go from speculation to speculation because it is an exceptional case". And who asks, moreover, to be confirmed.