Basic epidemiological parameter values from data of real-world in mega-cities: the characteristics of COVID-19 in Beijing, China

Abstract Background. With the spread of SARS-CoV-2 worldwide, understanding the basic epidemiological parameter values of COVID-19 from real-world data in mata-cities is essential for disease prevention and control. Methods. To investigate the epidemiological parameters in SARS-CoV-2 infected cases in Beijing, we studied all confirmed cases and close contacts in Beijing from 1 Jan to 3 Apr 2020. The epidemiological and virological characteristics were analyzed. Results. A total of 602 cases were positive for SARS-CoV-2, including 585 confirmed case-patients and 17 asymptomatic infections. The imported cases were mainly from Wuhan and then predominantly from abroad. Among 585 confirmed case-patients, the median age was 39 years. About 13.68% were severe and critical patients. The mean incubation period was 6.31 days. The secondary attack rate among households was higher than social contacts (15.55 vs.4.56%). The secondary attack rate of healthcare workers (HCWs) was higher than non-HCWs’ (7.26 vs. 4.24%). The basic reproduction number was 2.0, and the average serial interval was 7.64 days. No significant genetic variant was found. Conclusions. The transmissibility of SARS-CoV-2 was relatively high, especially among households and from HCWs, which should be focused on. So far, there is no evidence of widespread circulation of SARS-CoV-2 in communities in Beijing.