. 2020 Aug; 169: 106026.
Published online 2020 May 13. doi: 10.1016/j.rmed.2020.106026
PMCID: PMC7219423
PMID: 32405162

A study on infectivity of asymptomatic SARS-CoV-2 carriers

Associated Data



An ongoing outbreak of coronavirus disease 2019 (COVID-19) has spread around the world. It is debatable whether asymptomatic COVID-19 virus carriers are contagious. We report here a case of the asymptomatic patient and present clinical characteristics of 455 contacts, which aims to study the infectivity of asymptomatic carriers.

Material and methods

455 contacts who were exposed to the asymptomatic COVID-19 virus carrier became the subjects of our research. They were divided into three groups: 35 patients, 196 family members and 224 hospital staffs. We extracted their epidemiological information, clinical records, auxiliary examination results and therapeutic schedules.


The median contact time for patients was four days and that for family members was five days. Cardiovascular disease accounted for 25% among original diseases of patients. Apart from hospital staffs, both patients and family members were isolated medically. During the quarantine, seven patients plus one family member appeared new respiratory symptoms, where fever was the most common one. The blood counts in most contacts were within a normal range. All CT images showed no sign of COVID-19 infection. No severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections was detected in 455 contacts by nucleic acid test.


In summary, all the 455 contacts were excluded from SARS-CoV-2 infection and we conclude that the infectivity of some asymptomatic SARS-CoV-2 carriers might be weak.



A sample of 455 people is nothing to sniff at.

But, similarly to the face-mask issue, the WHO is waffling.  After saying asymptomatic spread is very rare, they now state there’s still too much that’s unknown.  Still, 455 people exposed to an asymptomatic carrier and not one got ill says a lot.

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