The case definition of a possible case in use on 24 January was slightly adapted from the one provided by the World Health Organization (WHO), based on an epidemiological link to Wuhan, China and a severe lower acute respiratory disease. It is noteworthy that the first nine possible cases identified in France, including the three confirmed cases described here, displayed mild respiratory symptoms with no sign of severity at the time of diagnosis. Increasing evidence suggests that mild clinical symptoms could be more frequent in cases of COVID-19 than with SARS-CoV and MERS-CoV [5]. Therefore, the case definition in effect on 24 January lacked sensitivity. This was counter-balanced by a tendency from the infectious diseases specialists in charge of classification of suspected cases to privilege the exposure to Wuhan over the clinical presentation in their decision. However, we cannot exclude that some COVID-19 cases remained undetected in France because of the lack of sensitivity of our case definition. The clinical criteria were expanded on 4 February to include any lower acute respiratory disease and the epidemiological criterion was extended to the whole of China. At that time, the French laboratory capacities were reinforced from one to five laboratories able to perform the diagnostics for COVID-19. Further extension to all 38 referring hospital laboratories is expected by early to mid-February 2020. Santé publique France will deploy in early February the outbreak investigation tool developed by the WHO (Go.Data [6]) in order to facilitate case data management and contact tracing at the national and local level in France.