PT  - JOURNAL ARTICLE
AU  - Zhang, Yi
AU  - Muscatello, David
AU  - Tian, Yi
AU  - Chen, Yanwei
AU  - Li, Shuang
AU  - Duan, Wei
AU  - Ma, Chunna
AU  - Sun, Ying
AU  - Wu, Shuangsheng
AU  - Ge, Lin
AU  - Yang, Peng
AU  - Jia, Lei
AU  - Wang, Quanyi
AU  - MacIntyre, Chandini Raina
TI  - Role of presymptomatic transmission of COVID-19: evidence from Beijing, China
AID  - 10.1136/jech-2020-214635
DP  - 2021 Jan 01
TA  - Journal of Epidemiology and Community Health
PG  - 84--87
VI  - 75
IP  - 1
4099  - http://jech.bmj.com/content/75/1/84.short
4100  - http://jech.bmj.com/content/75/1/84.full
SO  - J Epidemiol Community Health2021 Jan 01; 75
AB  - Background The presymptomatic transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been documented in limited clusters, and it is predicted through modelling. However, there is a lack of evidence from observations with a large sample size.Methods We used data from meticulous contact tracing of people exposed to cases of SARS-CoV-2 to estimate the proportion of cases that result from the presymptomatic transmission of the virus in Beijing during January 2020 and February 2020.Results The results showed that presymptomatic transmission occurred in at least 15% of 100 secondary COVID-19 cases. The earliest presymptomatic contact event occurred 5 days prior to the index case’s onset of symptoms, and this occurred in two clusters.Conclusions The finding suggested that the contact tracing period should be earlier and highlighted the importance of preventing transmission opportunities well before the onset of symptoms.