The new coronavirus continues to circulate and the clusters are proof of this. Whether they are triggered in departments classified as green - like in Dordogne and in Vienne in recent days -, or in countries emerging from the epidemic - South Korea, China -, they remind us that SARS-CoV-2 is always present. But they are also a sign that the health situation has improved.
What is a cluster?
A cluster is an Anglo-Saxon term which designates, according to the definition of the Ministry of Health, "an area for grouping cases". With more details, Public Health France evokes a "regrouping in time and space of cases of diseases, symptoms or health events within a localized population".
In French, we speak of an epidemic focus. "I prefer this expression, it allows in particular to make the analogy with fire", judge Michèle Legeas, teacher at the School of Advanced Studies in Public Health (EHESP), specialist in the analysis and management of situations in sanitary risks.
For the clusters that have appeared in recent days in France - at Clamart (Hauts-de-Seine), in Dordogne, in Vendée and in Vienne - "we are in small homes and, as in a fire, as long as the firefighters see smoke and the fire is small, they can put it out quickly, ”explains Michèle Legeas.
“On the other hand, if the outbreak starts in a dense forest, full of brush, distant, or that several foci join, the fire will be more important and will risk spreading throughout the forest. It will no longer be a matter of extinguishing a single start of fire, but a whole fire. It's the epidemic. "
How are they identified and treated?
The objective, therefore, is to see the smoke as early as possible to extinguish the fire immediately. The tests serve as watchtowers for the health authorities, who will then isolate the patients and their contact cases. "We know how to spot clusters," repeated Olivier Véran, Minister of Health, this Monday morning on BFMTV-RMC. When there are a certain number of patients, an investigation is made to wind up the chain and prevent it from spreading. "
In Clamart, for example, the last cluster to appear in France, an agent from a home for young workers fell ill and was detected positive for the new coronavirus this weekend. Everyone in the home has been tested or will be tested on Monday. The first results already show that at least seven other individuals are infected. People who have been in contact with these patients will be isolated in turn. With this method, the health authorities hope to limit the contagion.
Why are they appearing now?
Remember: when was the term cluster most used? In the very first phase of the epidemic, when the health authorities could still count the least serious cases and the hospitals were not yet overloaded with patients of Covid-19.
The outbreak of epidemic outbreaks is therefore a good sign. "It shows that containment has been effective, since we are once again interested in people with mild symptoms", explains Michèle Legeas.
Why are they going to multiply?
If the last known clusters were born in a still confined France, they should be more numerous after the deconfinement. The latter “increases the number of possible meetings, thus increasing the risk of catching and circulating the Covid. It makes sense, ”recalls epidemiologist Catherine Hill, former head of the biostatistics and epidemiology department at the Gustave Roussy Institute in Villejuif (Val-de-Marne).
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"New gatherings will occur, teachers arrive, school life assistants, traders ... All it takes is a contaminated person, and not necessarily symptomatic, to start a new outbreak," details the epidemiologist, who recalls that the asymptomatic levels for SARS-CoV-2 is "very important". "About 50% of those infected do not report symptoms," she said, citing a study by scientists from the Scripps Translational Science Institute.
At the same time, France aims to carry out 700,000 tests per week. The number of positive cases should therefore also increase. "The more we test, the more we will find positive people who will have infected others," said Catherine Hill.
How to avoid them?
Not everyone agrees on this point. Catherine Hill is quite alarmist. “With this virus, it is a race against time. You have to go very fast in terms of tests, find people, isolate them. As soon as someone goes back to work, it should be tested, it's the only solution, she insists. It is a contagious disease, if you just look for the symptoms, it is not enough. "
Michèle Legeas believes that it would not make sense to "test everyone, all the time". "Either we absolutely prevent the virus from circulating, but we might as well put ourselves in sterile bubbles ... Either we avoid the saturation of hospitals and, for that, we protect fragile people", she explains.
To prevent epidemic outbreaks from turning into real fires, "we must remain reasonable" during deconfinement, continues the teacher of the EHESP. "Do not meet with more than ten people, do not have intense and lasting contacts in a closed community, respect barrier gestures, wear a mask ... In short, as we do not know who around us is a fragile person, everyone must consider himself the spark capable of starting a new home. "