BACKGROUND: The transmission of COVID-19 is about to come under control within China, however, an emerging challenge to the Chinese authorities is reverse transmission due to COVID-19 patients/carriers evacuating from overseas to China. METHODS: We analysed the epidemiological characteristics of 311 Chinese citizens evacuated from Iran. All confirmed COVID-19 cases amongst the returnees were displayed by the spatial distribution pattern of the extent of COVID-19 infection. RESULTS: Characteristics that differed significantly amongst these returnees compared to the original infected cohorts in Gansu were mean age, occupation and sex. Differences observed between infected patients and non-patients amongst returnees were age, sex, race, occupation, the use of facemasks, and residential situation in Iran. The clinical features that were significantly related to infection were chill, shortness of breath, chest pain and nausea. Spatial distribution pattern analysis indicated that infected returnees had resided within Iranian provinces that had experienced high levels of COVID-19. The spatial distribution of the original homes of these returnees before departure for Iran demonstrated that returnees will largely return to northwest China, to regions that have only experienced low levels of infection within China. CONCLUSION: Blocking the reverse transmission of COVID-19 is critical in preventing a secondary outbreak of COVID-19.
The epidemiology of reverse transmission of COVID-19 in Gansu Province, China