Int J Biol Sci 2020; 16(15):2803-2811. doi:10.7150/ijbs.48991 This issue


COVID-19: Insight into the asymptomatic SARS-COV-2 infection and transmission

Dongsheng Han1,2,3*, Rui Li1,2,3*, Yanxi Han1,2,3, Rui Zhang1,3, Jinming Li1,2,3✉

1. National Center for Clinical Laboratories, Beijing Hospital, National Center of Gerontology; Institute of Geriatric Medicine, Chinese Academy of Medical Sciences, P.R. China.
2. Graduate School of Peking Union Medical College, Chinese Academy of Medical Sciences, Beijing, P.R. China.
3. Beijing Engineering Research Center of Laboratory Medicine, Beijing Hospital, Beijing, P.R. China.
*These authors contributed equally to the work.

This is an open access article distributed under the terms of the Creative Commons Attribution License ( See for full terms and conditions.
Han D, Li R, Han Y, Zhang R, Li J. COVID-19: Insight into the asymptomatic SARS-COV-2 infection and transmission. Int J Biol Sci 2020; 16(15):2803-2811. doi:10.7150/ijbs.48991. Available from

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Graphic abstract

The existence of a substantial but unclear number of asymptomatic SARS-COV-2 patients worldwide has raised concerns among global public health authorities. In this review, according to the published literature, we provided the evidence that asymptomatic infections can result in person-to-person transmission. Four studies suggested that the virus can be transmitted by asymptomatic patients for at least two consecutive generations, indicating its strong infectivity. Asymptomatic infection tends to be, but is not only, identified among young people (<20 years old). The majority of asymptomatic patients appear to have a milder clinical course during hospitalization, but the severity of the symptoms of the secondary patients infected by SARS-COV-2 from asymptomatic patients varies with their physical constitution. The proportion of asymptomatic individuals among all confirmed cases widely differed (from 1.95% to 87.9%) according to the study setting and the populations studied. The increasing large-scale tests are expected to give more information about the true number of asymptomatic infections in the population. In China and other countries, various guidelines for management of asymptomatic cases have been issued. Importantly, early detection, early reporting, early isolation and early treatment of asymptomatic patients require the joint efforts of policy makers, clinicians, technicians, epidemiologists, virologists and patients.

Keywords: SARS-COV-2, asymptomatic infection, serological assays, social distancing