SARS-CoV-2 is Mainly Distributed in Respiratory Droplets in the Exhaled Breath of COVID-19 Patients

Background: SARS-CoV-2 is released directly into the air through breathing by COVID-19 patients. Understanding the particle size distribution of SARS-CoV-2 in the exhaled breath of COVID-19 patients is essential for SARS-CoV-2 infection prevention policies.Methods: Here, serial nasopharyngeal swabs, exhaled breath specimens and environmental surface samples were collected at different days of COVID-19 patient hospitalization. Exhaled breath specimen collection was performed through a viral sampling tube and an air sampler. SARS-CoV-2 RNA detection was determined by real-time quantitative reverse transcription polymerase chain reaction (qRT–PCR). Results: We found that the COVID-19 patients exhaled ten million SARS-CoV-2 RNA copies per hour. The SARS-CoV-2 particles in the exhaled breath were mainly distributed in respiratory droplets (>4.7 μm), accounting for 87.14% of the total virus. There was a positive correlation between viral loads of nasopharyngeal swabs and exhaled breath specimens. The viral load of exhaled breath also showed a positive correlation with the viral load of environmental surface.Conclusions: SARS-CoV-2 in the exhaled breath of COVID-19 patients might be mainly transmitted via respiratory droplets. The viral load in the exhaled breath is determined by the viral load in the nasopharyngeal swab, and the viral load in the exhaled breath determines the presence and extent of environmental surface contamination. Therefore, the exhaled breath of COVID-19 patients plays a major role in the transmission of SARS-CoV-2.Funding: This research was supported by the National Major Research and Development Program(2020YFC0840800) and the National Natural Science Foundation of China (32000134) .Declaration of Interest: The authors declare no competing interests.Ethical Approval: Regarding the ethical requirements of human subjects, all specimen collections were obtained with the informed consent of the patients. None of the specimens recorded patient identifiers. The Ethics and Scientific Review Committee of Sierra Leone approved the study