ABSTRACT
We analyze data from the Fall 2020 pandemic response efforts at the University of Colorado Boulder (USA), where more than 72,500 saliva samples were tested for SARS-CoV-2 using quantitative RT-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 reported in symptomatic individuals. Regardless of symptomatic status, approximately 50% of individuals who test positive for SARS-CoV-2 seem to be in non-infectious 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 super-carriers and possibly also super-spreaders.
Subject(s)
COVID-19ABSTRACT
Up to 70% of SARS-CoV-2 infections in working- and school-age people are asymptomatic (Poletti et al., 2020), creating anxiety over reopening workplaces and schools around the world. In the absence of effective treatments or a vaccine, peace of mind will come only with community-based SARS-CoV-2 screening, where many people are tested on a regular basis. However, recent models show that short sample-to-answer turnaround time will be a critical property of effective screening strategies (Larremore et al., 2020). Here, we describe an RT-LAMP test for SARS-CoV-2 in raw saliva that takes about 45 minutes from sample to answer and requires only simple equipment (pipettes and a heating source). The assay has a limit of detection of 100 virions per microliter, and targets two separate regions of the SARS-CoV-2 genome. By combining rapid sample-to-answer turnaround time with the use of saliva, our RT-LAMP assay provides a low-complexity, portable, and robust system for real-time community screening.