Evaluating new evidence in the early dynamics of the novel coronavirus COVID-19 outbreak in Wuhan, China with real time domestic traffic and potential asymptomatic transmissions

Can Zhou

The original internationally exported cases used in Wu et al. (2020) contain 63 cases, of which 4 cases do not have a recent travel history to Wuhan and they were excluded from analysis. Additionally, one confirmed case in Germany infected through contacts with a patient from Wuhan (Rothe et al., 2020) , and it is also excluded here. A total of 58 confirmed cases from 14 countries/regions were used in this study. In this study, the author adopts the same case definition as in Wu et al. (2020) : a case is an individual that show symptoms, which can be detected by temperature screenings, or severe enough to require hospitalization, plus a recent travel history to Wuhan. In Wu et al. (2020) , the symptom onset date was used as the date of exportation. However, the onset date does not always coincide with the date of travel from Wuhan. In this study, the date of exportation is defined as the date the individual exits Wuhan (local time, 49 cases), and when the exit date is not available, the symptom onset date was used (4 cases), and when both the exit date and the onset date were not available, the confirmation date was used instead (4 cases). The export dates fall between Dec. 31, 2019 and Jan. 29, 2019. Of the 40 cases, on which both the date existing Wuhan and the symptom onset date were available, 57.5% (23 cases) were asymptomatic when leaving Wuhan, 25% (10 cases) developed symptoms before leaving Wuhan, and 17.5% (7 cases) developed symptoms on the same date when leaving Wuhan.