A novel coronavirus disease, designated as COVID-19, has become a pandemic 
worldwide. This study aims to estimate the incubation period and serial interval 
of COVID-19. We collected contact tracing data in a municipality in Hubei 
province during a full outbreak period. The date of infection and 
infector-infectee pairs were inferred from the history of travel in Wuhan or 
exposed to confirmed cases. The incubation periods and serial intervals were 
estimated using parametric accelerated failure time models, accounting for 
interval censoring of the exposures. Our estimated median incubation period of 
COVID-19 is 5.4 days (bootstrapped 95% confidence interval (CI) 4.8-6.0), and 
the 2.5th and 97.5th percentiles are 1 and 15 days, respectively; while the 
estimated serial interval of COVID-19 falls within the range of -4 to 13 days 
with 95% confidence and has a median of 4.6 days (95% CI 3.7-5.5). Ninety-five 
per cent of symptomatic cases showed symptoms by 13.7 days (95% CI 12.5-14.9). 
The incubation periods and serial intervals were not significantly different 
between male and female, and among age groups. Our results suggest a 
considerable proportion of secondary transmission occurred prior to symptom 
onset. And the current practice of 14-day quarantine period in many regions is 
reasonable.