Serial Interval and Reproductive Number of COVID-19 among 116 Infector-infectee Pairs - Jingzhou City, Hubei Province, China, 2020.

WHAT IS ALREADY KNOWN ABOUT THIS TOPIC?:The key epidemiological parameters including serial interval, basic reproductive number (R 0), and effective reproductive number (R t) are crucial for coronavirus disease 2019 (COVID-19) control and prevention. Previous studies provided different estimations but were often flawed by some limitations such as insufficient sample size and selection bias.WHAT IS ADDED BY THIS REPORT?:In this study, a total of 116 infector-infectee pairs meeting strict inclusion criteria were selected for analysis. The mean serial interval of COVID-19 was 5.81 days (standard deviation: 3.24). The estimated mean with 95% confidence interval of R 0 was 3.39 (3.07-3.75) and 2.98 (2.62-3.38) using exponential growth (EG) and maximum likelihood (ML) methods, respectively. The R t in the early phase of the epidemic was above 1 with the peak of 4.43 occurring on January 8, and then showing subsequent declines and approaching 1 on January 24.WHAT ARE THE IMPLICATIONS FOR PUBLIC HEALTH PRACTICES?:This study supports previous findings that COVID-19 has high transmissibility and that implementing comprehensive measures is effective in controlling the COVID-19 outbreak.