what we have learned and what we do not yet know

Just over two months after the start of the Covid-19 epidemic, the sharing of scientific data on a scale and at an unprecedented speed makes it possible to lift part of the veil on this form of respiratory infection and on SARS- CoV-2, the new coronavirus responsible for it, but only part of it.

• Do we know the origin of the virus?

It is well established that the disease is caused by this previously unknown virus, but the origin of SARS-CoV-2 is not known with certainty. It seems to have for ancestor a coronavirus found in bats, which would be common with its cousin responsible for SARS (the abbreviation in English for severe acute respiratory syndrome or SARS).

SARS-CoV-2 is very similar to a coronavirus hosted by another mammal, the pangolin, in the region through which it binds and infects host cells. It is likely that the bat coronavirus would have passed through an intermediate host, a priori the pangolin, by evolving genetically, then that this virus, after further mutations, would have become able to infect humans.

However, the circumstances under which SARS-CoV reached the man are still unknown. The epidemic was discovered with cases clustered around the Huanan Seafood Wholesale Market in Wuhan, but we have learned since the existence of a few previous cases in people who had not attended it.

• What do we know about Covid-19 disease?

The average incubation time between contamination and the onset of symptoms is around six days. It can go up to twelve days, hence the choice to isolate people who have been in contact with an infected subject for fourteen days. With a few exceptions, the overwhelming majority of cases of contamination have occurred through contact with people who already have manifestations of the disease.

The Chinese Center for Disease Control (CCDC) has published the characteristics of a large number of patients, three-quarters of them in Hubei Province, including nearly 45,000 laboratory-confirmed cases. This article gives a more precise idea of ​​this infection.

It is considered benign in 80% of cases and seems fatal to 2% of those infected. Those who die are quite old: 80% of them are at least 60 years old. None of the 416 infected children under the age of 10 died. The existence of a pre-existing pathology greatly increases the fatality rate: it is 0.9% in otherwise healthy people but jumps to 10% in the presence of cardiovascular disease, to 7% in case of diabetes and 6% if the patient has a chronic respiratory disease.

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