Epidemiological characteristics of COVID-19 in Shenzhen, China: comparison between imported and local cases.

Introduction: An unprecedented outbreak of the novel coronavirus disease (COVID-19) has swept across the globe since the end of 2019. Shenzhen confirmed its first imported case from Wuhan on 19 January 2020. However, little is known regarding the epidemiological characteristics of COVID-19 in these imported cities. Methodology: Data of all 417 confirmed cases diagnosed in Shenzhen before 29 February were collected. The epidemiological characteristics of imported and local cases were compared. The resilience to COVID-19 was evaluated by discharge density. Results: All ten districts reported COVID-19 cases by 29 February, including 331 imported and 86 local cases. The Pearson linear correlation model showed the number of confirmed cases (r = 0.990, p < 0.001) as well as incidence of COVID-19 (r = 0.766, p = 0.010) was positively correlated with the gross domestic product of district. Family clusters were more commonly found in local cases. Imported patients had earlier onset (p < 0.001) and diagnosis (p < 0.001), but longer interval from onset to admission (p = 0.030), diagnosis (p = 0.003) and discharge (p = 0.016). Older and severe cases had lower discharge density (0.024 and 0.018, respectively); while cases with subclinical symptoms exhibited higher discharge density (0.052). Conclusions: COVID-19 patients were predominantly imported cases in Shenzhen and the spatial distribution was closely related to district GDP. Imported and local cases differed in the intervals from onset to admission, diagnosis and discharge. Moreover, family-based transmission should not be ignored, especially in local cases.