Three months ago, with the first information about the new coronavirus that appeared in Wuhan, China, the international medical and scientific community entered an unknown land, where questions are emerging at a rapid pace. Here are some of the questions about the Covid-19 epidemic for which research does not yet provide answers, but at best hypotheses.
1. What animal is it behind the virus?
The coronavirus at the origin of Covid-19, which appeared on a fish market in which meat was also sold under the coat, is said to have been transmitted to humans by a pangolin, via a bat. . The story is known ... "but it is still an hypothesis, advanced, but not yet verified, explains François Bricaire, former head of the infectious diseases department at the Pitié-Salpêtrière hospital in Paris. Veterinarians will have to work on the subject. A crucial mission: better understanding the transmission of coronaviruses from animals to humans is essential to prevent the emergence of new pandemics.
2. Is the Covid-19 sensitive to the seasons?
"We don't know anything about the seasonality of the virus or its ability to return," insists Frédéric Tangy, a researcher at the vaccine innovation laboratory at the Institut Pasteur. Unlike influenza viruses, which thrive with winter, "coronaviruses can come out in any season," said the scientist. The proof: in 2012, the Sea was born in Saudi Arabia by more than 40 degrees in the shade ... And the current development of the pandemic in Africa would also tend to prove that the heat does not prevent the disease from running. "We should also expect a second wave, in the fall, that's what we are preparing for in the search for the vaccine," said Frédéric Tangy. It is estimated that 60% or even 70% of the population must be immunized for the virus to stop circulating. "
3. How long are sick people contagious?
Research has already shown that patients are contagious before the first symptoms appear. But how long? "At least 48 hours," says François Bricaire, when Frédéric Tangy expects "four to seven days". After the disappearance of the cough or fever, the patients continue to excrete the virus, but "we do not know this aspect very well", recognizes the researcher. "Patients shed the virus for 6 to 12 days, and in others it can go up to 20 days, without knowing whether the virus continues to be virulent enough to be transmitted, or not," says François Bricaire. Another question mark, and of size: in the absence of systematic tests, "we have no idea of the number of healthy carriers, who ignore being contagious", adds the professor.