- The number of additional cases of Covid-19 in 24 hours is around 5,000, while the number of deaths remains below 20, according to the latest figures from the DGS.
- An astonishing curve, which suggests that, perhaps, this coronavirus would have become less virulent.
- It is still too early to know if the number of deaths will remain low during the coming months, especially with the temperatures which will drop and the re-entry, but two experts, one epidemiologist, the other modeler, help us to see more. clear.
Nearly 4,900 positive cases for the coronavirus and only one additional death in 24 hours. The figures unveiled by the DGS on Sunday evening confirm the trend of this last week: contaminations are increasing rapidly. But the number of deaths, on the other hand, remains low and stable, as do hospitalizations in intensive care.
Some deduce that the coronavirus has lost its dangerousness. Are we doing too much? Or, on the contrary, will we regret in a few months not having learned the lessons of the first wave?
A mutation ?
Several leads can shed light on this discrepancy between the number of cases and the number of deaths. Among these, the Sars-CoV-2 virus is said to be less virulent. A hypothesis which is based in particular on a study by British-American researchers published in the scientific journal Cell on July 2, which highlights a mutation of Sars-CoV-2 which would have made it more infectious. Does this mean that it would be more contagious, but less virulent? Infectious diseases urge the greatest caution. First of all because this laboratory work must be supplemented by other studies, in particular on living beings. “It is not because a virus mutates that it fundamentally changes things in terms of virulence, warns Mircea Sofonea, lecturer in epidemiology at the University of Montpellier. In addition, the variants [the new forms of the coronavirus observed today] observed in this study had been present for several months in Europe. They have therefore already participated in the first wave. There was no change in the coronavirus during the summer that changed its lethality. "
This hypothesis does not convince either the Minister of Health, who has not ceased this summer to call for vigilance and respect for barrier gestures: “no scientific argument comes to support this theory, alas, thus swept away Olivier Véran in the JDD . The Covid that is spreading is the same as that which claimed the lives of 30,000 French people. "
Some doctors warn that the curve of deaths linked to the coronavirus is likely to join the surge in detected cases. Indeed, many recall that the virus takes a few weeks before sending some patients to intensive care. "Virulence and contagiousness can be decorrelated, because their expression does not take place at the same time (the peak of contagiousness takes place one day before the expression of symptoms, but the deterioration of the state occurs on average three weeks after the symptoms ), nor in the same organs, since contagiousness is due to replication in the pharynx and virulence is expressed in the lungs ”, synthesizes Mircea Sofonea.
The question of testing
Difficult, therefore, to know if these low deaths should invite the greatest caution or optimism ... Some think that if only the number of cases is increasing, it is simply because we are testing more. It is true that we went from 50,000 tests per day in early July to more than 100,000 daily since August 14, but we note that the positivity rate (number of positive cases out of 100 people tested) reached 3.4% on August 21, compared to 1.6% on August 6. "Over the last two weeks in Ile-de-France, we note that the positivity rate has increased by 42% while the number of tests is stable", underlines Jean-Stéphane Dhersin, modeler and deputy scientific director of the National Institute mathematical sciences and their interactions from the CNRS. Who adds: “During the first wave, we did not have the testing capacity that we have today. People were only tested in the hospital. At the time, patients with Covid 19 were mainly elderly. It is therefore possible that the graph we are reading today approaches the hypothetical diagram that we would have had at the beginning of March if we had been able to randomly test the French population.
Less fatal?
For the moment, therefore, there is nothing to ensure that the coronavirus would be less virulent. Will this potential second wave be less deadly? "That's another question", nuance Mircea Sofonea. Which lists two avenues for reflection. First, patient care has improved in recent months. “With hindsight, experience, refined knowledge, currently unsaturated services, we take better care of, says the epidemiologist. It was noted that the mortality recorded in the intensive care units reached 24% from the start of the epidemic until the end of April, and has dropped to 19% between the start of the epidemic and today. Resuscitators tell us that they are more successful in avoiding intubation. "
Second parameter to take into account: the age of the patients. We now know that a large proportion of new cases are young. “The proportion of 20/40 year olds among infected people increased during the summer, while the contribution of older people, who are more at risk, decreased,” summarizes the epidemiologist. Which has an effect on lethality. "An impact that can only be imagined lasting on condition that these infected people do not infect elderly or fragile people ... We should therefore, in the coming days, keep an eye on the age of those infected.
Lots of unknowns in the coming period
“Last week, there were around 20 deaths per day, it is as much as on March 16, that is to say the day before confinement. We are not on ridiculous figures! There is a rebound in cases which can turn into a second wave if there is no change in the dynamics, either by a collective reappropriation of barrier gestures, or by political decisions of localized reconfiguration. But without falling into too much pessimism either. This keeping of the epidemic under control, it was already seen in June: the R0 was then less than 1 and yet, we were deconfined and school had resumed. "
And Mircea Sofonea to explain why the period which opens includes many unknowns which prohibit any prediction. “The start of the school year is risky from a health point of view because there is a lot of mixing with the return from leave, the return to school, trips to work. And the cold season which favors epidemics because of groupings in closed environments and nasal mucous membranes, barrier against viruses, which are less effective when it is cold and dry. As well, the models are relatively efficient when the parameters are constant (same mobility, same temperature, same health precaution), as soon as there is a change, it is difficult to imagine what will happen next. "
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