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.