Epidemiological parameters of coronavirus disease 2019: a pooled analysis of publicly reported individual data of 1155 cases from seven countries

Shujuan Ma; Jiayue Zhang; Minyan Zeng; Qingping Yun; Wei Guo; Yixiang Zheng; Shi Zhao; Maggie H Wang; Zuyao Yang

Despite the explosive growth of the number of studies on COVID-19, several key epidemiological parameters of the disease remain to be clarified, among which are incubation period and serial interval. The two parameters have important implications for the monitoring, surveillance and control of infectious disease. The mean or median incubation period and serial interval estimated by previous studies were mostly 4 to 5 days, 2-7 and 4 to 4.5 days, [8] [9] [10] [11] [12] respectively. While some of the studies included only a limited number of cases (around or less than 100), 2, 4, 6, 7, [9] [10] [11] [12] others might have suffered from inaccuracy of original data. For example, in some studies, most cases had a long or even unclear interval of exposure, making it difficult to determine the exact exposure date 3, 5, 13 and giving rise to error. Besides, the order of transmission (i.e., who is infector and who is infectee) in clustering cases, which is crucial to estimation of both parameters, is easy to be mistaken given the possibility of pre-symptomatic and asymptomatic transmission, [14] [15] [16] [17] but previous studies rarely described how this issue was handled.