[Epidemiological study design of asymptomatic infection of the 2019 novel coronavirus]

COVID-19 is caused by the 2019 novel coronavirus (2019-nCoV). COVID-19 clinical cases are considered as the principal source of infection, however, asymptomatic cases may also play a role in the transmission. Significant gap exists in terms of the proportion or prevalence and transmissibility of asymptomatic cases. This study design plans to use data from areas with different epidemiological profiles to investigate the COVID-19 epidemic in China. In each selected region, both general community residents and key populations at high risk of COVID-19 infection, including recovered COVID-19 cases, close contacts of confirmed COVID-19 cases, medical professionals, investigators at CDCs, and visitors to fever clinics, will be recruited and examined for viral RNA of 2019-nCoV and serum antibodies. Prevalence and characterization of asymptomatic cases will be determined, stratified by varied demographics and exposure risk. During the follow-up, the change in the serum antibodies will be studied prospectively in the symptomatic and asymptomatic cases to address the scientific and public health concerns of infectivity and transmissibility of 2019-nCoV.