Cross-sectional assessment of SARS-CoV-2 viral load by symptom status in Massachusetts congregate living facilities

J Infect Dis. 2021 Jul 13;jiab367. doi: 10.1093/infdis/jiab367. Online ahead of print.


Transmission of COVID-19 from people without symptoms confounds societal mitigation strategies. From April to June 2020, we tested nasopharyngeal swabs by RT-qPCR from 15,514 staff and 16,966 residents of nursing homes and assisted living facilities in Massachusetts. Cycle threshold (Ct) distributions were very similar between populations with (N = 739) and without (N = 2179) symptoms at the time of sampling (mean Ct 25.7 versus 26.4, ranges 12-38). However, as local cases waned, those without symptoms shifted towards higher Ct. With such similar viral load distributions, existing testing modalities should perform comparably regardless of symptoms, contingent upon time since infection.

Keywords: COVID-19; SARS-CoV-2; molecular diagnostics; symptoms; viral load.