Detection and quantification of infectious severe acute respiratory coronavirus-2 in diverse clinical and environmental samples

To explore the potential modes of Severe Acute Respiratory Coronavirus-2 (SARS-CoV-2) transmission, we collected 535 diverse clinical and environmental samples from 75 infected hospitalized and community patients. Infectious SARS-CoV-2 with quantitative burdens varying from 5 plaque-forming units/mL (PFU/mL) up to 1.0 x 10(6) PFU/mL was detected in 151/459 (33%) of the specimens assayed and up to 1.3 x 10(6) PFU/mL on fomites with confirmation by plaque morphology, PCR, immunohistochemistry, and/or sequencing. Infectious virus in clinical and associated environmental samples correlated with time since symptom onset with no detection after 7-8 days in immunocompetent hosts and with N-gene based C-t values <= 25 significantly predictive of yielding plaques in culture. SARS-CoV-2 isolated from patient respiratory tract samples caused illness in a hamster model with a minimum infectious dose of <= 14 PFU. Together, our findings offer compelling evidence that large respiratory droplet and contact (direct and indirect i.e., fomites) are important modes of SARS-CoV-2 transmission.

Automated summary

This study explored the potential modes of SARS-CoV-2 transmission and found that large respiratory droplets and contact (direct and indirect) are important modes of transmission. The presence of infectious virus in clinical and environmental samples correlated with time since symptom onset and the ability to yield plaques in culture.