During the weekend of February 22-23, 2020, the epidemic situation evolved worldwide with the intensification of outbreaks in South Korea, Japan and Singapore, and the appearance of new outbreaks in Iran and Italy. In these countries, we are witnessing a community transmission with no identified link with cases imported from China. This situation raises many questions. How is the disease diagnosed? What is the period of contagiousness? How long is the incubation? Etc. Here are the answers of the Institut Pasteur.
In December 2019, an outbreak of apparently viral pneumonia of unknown etiology emerged in the city of Wuhan, in the Chinese province of Hubei. A novel coronavirus (SARS-CoV-2) is the pathogen responsible for this infectious respiratory disease called Covid-19 (CoronaVIrus Disease).
How is Covid-19 diagnosed in patients?
The diagnosis is suspected in front of signs of respiratory infection in a person returning from a place where the virus circulates, in the 14 days preceding the symptoms onset, according to the case definition of Santé publique France.
What is the period of contagiousness?
Contagiousness seems to start with the appearance of symptoms, even a few days before for some people. This period of contagiousness would last longer in symptomatic people, especially when they cough.
How long is the incubation?
The duration of incubation is an average of 5 to 6 days, with extremes of 2 to 12 days, which justifies the quarantine period of 14 days.
Can the virus survive in the environment? And if so, for how long?
According to the available data, the survival of coronaviruses in the outdoor environment is only a few hours on dry inert surfaces. Given duration and conditions of transport between France and China, the risk of becoming infected with SARS-CoV-2 by touching an object imported from China is considered extremely low. Standard hygiene measures (hand washing, surface cleaning) are effective.
What is the animal reservoir?
A virus, 96% identical to SARS-CoV-2, has been identified in bats captured in China. The bat is therefore most likely the reservoir of the virus.
How is the virus transmitted from animals to humans?
It is likely that a mammal served as an intermediate host between the bat and man. This intermediate animal is not identified with certainty, but the pangolin is suspected.
This series of questions and answers was conducted on Wednesday February 26, 2020, morning.
International research efforts are continuing, including at the Institut Pasteur in Paris and in the Institut Pasteur International Network, to clarify the answers to these questions.
Covid-19 video: what we have learnt as of February 20, 2020 - With Arnaud Fontanet, epidemiologist at the Institut Pasteur (Paris)
This study is part of the priority scientific area Emerging infectious diseases of the Institut Pasteur's strategic plan for 2019-2023.