A queue to buy protective masks in Wuhan (China), the epicenter of the coronavirus, on February 1, 2020. – Philip FONG / AFP
- “Super-spreaders” carrying Covid-19 have been identified in South Korea, Mulhouse (Alsace) or even at Contamines-Montjoie (Haute-Savoie).
- When individuals with a virus infect an average of one or two people, these “super propagators” can transmit a virus to up to ten or 20 people.
- Frédéric Tangy, director of the vaccine innovation laboratory at the Pasteur Institute, explains to 20 minutes who are “super-spreaders” and why it’s impossible to spot them.
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In Austria, in a ski resort in Tyrol, but also in Haute-Savoie, in
Contamines-Montjoie, “super-spreaders” in
Covid-19 have been identified. Who are these people who can infect dozens of people and can we “detect” them? Lighting with
Frédéric Tangy, director of the vaccine innovation laboratory at the Pasteur Institute, which is currently working on a vaccine.
What is a “super-spreader”?
Individuals with a virus will infect one or two people on average, as is the case with Covid-19. “Super-spreaders” can transmit a virus to up to 10 or 20 people, on average as well. Their viral loads can go up, like Ebola, to tens of billions of infectious particles per milliliter.
At this point, we cannot yet explain why some people have such viral loads and secrete more viruses than others. We do know, however, that in some individuals viruses, such as Covid-19, grow better. They are too weak to be able to destroy the virus which multiplies without obstacle or do not even show symptoms continue to spread the virus without knowing it. There are no rules, except that which shows that a “super-spreader” who is alone at home will not infect anyone.
Is the phenomenon of “super propagators” new?
Vaccinology experts and all other experts in vector-borne disease modeling know that there are “index” individuals behind “clusters” [foyers d’infection]. The “super-spreaders” that we hear about today are not textbooks, with the exception of the Covid-19. We have already seen this during other sequences of spread of viral infections, with SARS, Ebola, AIDS or measles. In the 1970s in the United States, a man with measles had infected an entire amphitheater.
Have “super-spreaders” emerged since the start of the Covid-19 epidemic?
We had a case in Korea, another in Austria. In Mulhouse, too. And above all, we had this English in
holidays in Les Contamines-Montjoie. On his own, he was behind one of the first
“Clusters” in France. He was a “super-spreader” and propagated the Covid-19 in the ski resort. Twenty people were reportedly infected with the same individual. It remains to be seen how: if they were all contaminated at the same time, if they were all in the same place, etc.
Why can’t we spot them and isolate them?
The epidemiologists are working on it but it is a real police investigation. To be able to identify these “super-spreaders”, you have to go back to the propagation history, look for “contact cases” [combien d’individus ont été infectés] and if it is the same virus that circulated. For AIDS, for example, it was very difficult because the sequences of the virus varied from one individual to another, which is not the case at this stage for Covid-19.
As long as a “super-spreader” has not been isolated, studied in detail when it transmitted the virus, it is impossible to recognize it. Or else everyone should be screened for people with 100 times higher viral loads, but that is not possible. If the idea is to isolate these “super-spreaders” before they contact other individuals, it is impractical. We only noticea posteriori that an infectious person was a super propagating agent, only after an outbreak of infection was discovered.
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