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


Background: COVID-19 has spread around the globe. This study investigates the infectivity of asymptomatic carriers. 

Materials and methods: 455 contacts who were exposed to the asymptomatic COVID-19 positive virus carrier were the subjects of this study. 

Results: During quarantine seven members in contact with the asymptomatic individual developed new cardiovascular conditions. However, no SARS-CoV-2 infections were detectable in all 455 contacts by a nucleic acid test. 

Conclusion: All 455 contacts did not contract the virus and thus the researchers concluded that the infectivity of some asymptomatic SARS-CoV-2 carriers might be weak. 


As of March 24, 2020 there have been 334981 confirmed cases and 14652 deaths globally. The basic reproduction number of SARS-COV-2 is predicted to be between two and three, which is higher than SARS-CoV. It has been previously reported that asymptomatic carriers could still transmit the virus, but this is still a controversial topic. Here we report one case of an asymptomatic SARS-CoV-2 carrier with nosocomial infection and his 455 contacts.


A 22 year old female patient with a medical history of congenital heart disease. As Case A vitals stabilized she was transferred to the emergency department observation unit (EDOU). She was then tested by a nasopharyngeal swab where she tested positive for SARS-CoV-2 by real time Reverse transcription-Polymerase Chain Reaction (RT-PCR). The patient had not visited Wuhan lately and did not present with fever, sore throat, or other COVID-19 infection related symptoms. The patient's blood measurements remained within normal tolerances for white blood cells, lymphocytes, C-Reactive protein, and procalcitonin. Similarly, a chest computed tomography (CT) scan showed no COVID-19 imaging features. 

While in the hospital the patient received antiviral and interferon therapy and 11 days after treatment the chest CT showed no significant changes. The patient tested positive for 5 days and then on the 6th day she tested negative. She was released from quarantine on day 21 and released. Case A was diagnosed as an asymptomatic carrier. 

Materials and Methods 

This study considers an asymptomatic carrier as one who presents without clinical symptoms, but whose SARS-CoV-2 test remains positive. All contacts, staff, family members, and associates were routinely screened for infection. 


Patients in the ED

All abnormal CT findings were discussed by professional radiologists and confirmed to be of a non-viral origin. All patients in the EW were required to wear a mask except while eating or drinking. 

Family Members 

None tested positive for SARS-CoV-2 and all wore masks when in contact with Case A. The only time the mask was taken off was when eating or drinking. 


All staff wore proper protective equipment when interacting with Case A such as N95 respirators, isolation gowns, and goggles. 


All developed medical issues were related to underlying or preexisting medical conditions. Combined with proper protective equipment like masks the researchers conclude that there is no need to worry about asymptomatic individuals. The limitations of this study is that there is only one case in this study. 


Infectivity of some asymptomatic SARS-CoV-2 might be weak. Effective prevention is helpful to prevent COVID-19 spread of asymptomatic carriers. The results may alleviate public concern of asymptomatic spread.