Its profile, the way it acts, its targets, its Achilles heel ... Like experienced inspectors, scientists around the world are working to learn more about the Covid-19 coronavirus, in the hope of better combating it. What do we know about him? And on the contrary, what are its gray areas?
We asked three experts: Marie-Paule Kieny, virologist and former WHO Assistant Director-General; Jean-Claude Manuguerra, head of the emergency biological intervention unit at the Pasteur Institute (Cibu) and Jean-Stéphane Dhersin, mathematician at CNRS, specialist in epidemic modeling.
What family does he belong to?
Covid-19 is a coronavirus, a large family of viruses that have been believed to cause only colds for decades. In 2003, SARS was the first coronavirus to cause severe pneumonia in humans, before the Sea in 2012, then “our” Covid-19, responsible today for 5700 deaths worldwide.
"The disease developed on a live animal market in Wuhan, China," says Jean-Claude Manuguerra. It seems that a bat has infected a pangolin which has contaminated humans. But there is no absolute certainty on the pangolin! "
How is it transmitted?
"The virus is not the Chernobyl cloud, it does not circulate in the air, it is men who circulate it," insists Jean-Stéphane Dhersin. There are two known modes of contamination. The inhalation of droplets emitted by a patient who coughs, sneezes or sputters. "Or by touching an infected surface and then bringing our hands to our face, which we do by reflex very often," adds Dr. Manuguerra.
The tough virus can stay alive for several hours on plastic, steel (our door handles), cardboard, copper, etc. To protect yourself, two solutions: keep your distance from others as much as possible (hence the school closings, bars, restaurants in France) and wash your hands very regularly.
VIDEO. How to wash your hands well in 6 steps
Is stomach ache a symptom?
The coronavirus attacks the respiratory system. "It causes in 60% of cases of cough, in 98.6% of fever, in 70% of fatigue," says Marie-Paule Kieny. What about stomach aches, the noise of which has been circulating for a few days that they could be a sign?
“You can have it when you are infected, but - for now - these are not typical symptoms of the disease. Without fever or cough, it's probably not the coronavirus. Just as a sore nose and a sore throat are more the sign of a cold or a sore throat, ”continues the virologist.
What does being “asymptomatic” mean?
That one can be infected with the coronavirus without feeling the symptoms or so weakly that one does not notice them. "There may be asymptomatic forms in children, as in adults, but these visibly participate in the spread of the virus," notes the expert. Today, it is not known how many people are asymptomatic. It is only by carrying out antibody tests in the general population that we will be able to know how many people have been infected. This may be done in a second step. The Chinese have started. "
If I am infected, how many people will I infect in my turn?
"Between 2.3 and 3 (against 1.3 for the flu) and each will reinfect the same number within 5 to 6 days of contamination," says Jean-Claude Manuguerra. “Depending on the number of contacts I have, this can go very quickly. In South Korea, a patient is said to have infected at least 43 others, ”adds Jean-Stéphane Dhersin.
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Hence the barrier measures to bring down what is called in the jargon the "R0". “What we saw in Wuhan is that they allowed to go from 3 to 1 infected person. However, below 1, we no longer speak of an epidemic, ”decrypts Jean-Claude Manugerra.
Is it very deadly?
98% of patients will recover from coronavirus. 80% will have mild symptoms, 15% a severe form such as pneumonia, 5% a critical form. "The lethality, that is to say the number of deaths compared to the number of cases is now 2% and this is probably overestimated," reassures the researcher from Pasteur.
For the time being, it is age and the presence of other diseases (cardiac, for example) that increase the risk of having a serious form. But for several days, an increase in the number of younger people has been observed in the intensive care units in France. Of the 300 patients who are currently hospitalized there, half are under the age of 60. Good news, however: children continue to be spared from the Covid-19.
Why should we be wary of the "eighth day"?
“There is a possible worsening of symptoms around the eighth day. If you are infected, you must therefore be attentive throughout the duration of the illness and do not relax your attention on the 4th or 5th day. Clearly, we are careful, "advocates Marie-Paule Kieny. The woman who has spent part of her career at the WHO explains this change by triggering an immune response "which can do damage" in addition to that of the virus itself.
VIDEO. Coronavirus: the pandemic explained by a specialist
Can the virus mutate?
"But viruses, like the flu, mutate all the time!" For the coronavirus, there are also mutations but, for the moment, none of them changes its severity or the way it attaches to human cells, which is reassuring, ”deciphered the virologist. Around the world, Covid-19 is being watched like milk on fire to check that this situation does not change.
Can I have it twice?
The question is all the more important since a case in Asia of "reinfection" had been raised. "The answer seems to be no, and so much the better," says Marie-Paule Kieny. This patient probably left the hospital with a viral load. The Chinese have conducted animal studies and animals do not contract the disease. This goes for the short time. No one knows if you can get infected again a few months later. "
How are we going to treat him?
"I don't like to hear that there is no treatment," says Jean-Claude Manuguerra. The risk is to worry the population. I prefer to say that there is no specific one for coronavirus. Oxygen if the situation worsens, ventilation ... These are treatments to get over it and get better! "
For the rest, several research avenues have been launched, notably in Pasteur's laboratories. Objective: find a vaccine. At the same time, we are working to find an effective medication among the existing ones. Antivirals will be particularly scrutinized with the setting up of a European clinical trial bringing together 3,200 patients, including 800 in France.
How many people are likely to be infected in France?
The coronavirus epidemic will "probably" affect more than half of the French population, reacted this Sunday morning Jean-Michel Blanquer the Minister of Education. "Ultimately, that is to say in several months," says Jean-Stéphane Dhersin, the mathematician who no longer excludes seeing 10, 15 or even 20 million French people affected.
“The idea is to spread the epidemic over time to avoid a brutal peak which would create saturation in hospitals. Will the drastic measures taken by the government help to soften the curves? Yes, he is convinced.
But for the specialist to warn us: "The French say to themselves: we are forced to do so, we need results. However, in the coming days, cases will continue to increase rapidly. It makes sense. The effects of the measures will be felt, but not for a week or two. You have to be patient. "
How long can the epidemic last?
They say it in chorus: they would like to answer but no one is capable today. Especially since there will inevitably be a revival. The weather, bringing hope is scrutinized: respiratory diseases are not fond of sunny days. In any case, notes Jean-Claude Manuguerra, “Epidemics always have an end. "
