Just 2% of SARS-CoV-2-positive individuals carry 90% of the virus circulating in communities

We analyze data from the fall 2020 pandemic response efforts at the University of Colorado Boulder, where more than 72,500 saliva samples were tested for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) using qRT-PCR. All samples were collected from individuals who reported no symptoms associated with COVID-19 on the day of collection. From these, 1,405 positive cases were identified. The distribution of viral loads within these asymptomatic individuals was indistinguishable from what has been previously observed in symptomatic individuals. Regardless of symptomatic status, similar to 50% of individuals who test positive for SARS-CoV-2 seem to be in noninfectious phases of the disease, based on having low viral loads in a range from which live virus has rarely been isolated. We find that, at any given time, just 2% of individuals carry 90% of the virions circulating within communities, serving as viral supercarriers and possibly also superspreaders.

Automated summary

The study found that even asymptomatic individuals with SARS-CoV-2 may have low viral loads that are not infectious. Moreover, only 2% of individuals are responsible for carrying 90% of the virions circulating within communities, potentially acting as viral supercarriers and superspreaders.