Severe acute respiratory syndrome coronavirus 2 can be detected in exhaled aerosol sampled during a few minutes of breathing or coughing.

BACKGROUND: The knowledge on the concentration of viral particles in exhaled breath is limited. The aim of this study was to explore if severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can be detected in aerosol from subjects with the coronavirus disease 2019 (COVID-19) during various types of breathing and coughing and how infection with SARS-CoV-2 may influence the number and size of exhaled aerosol particles.

METHODS: We counted and collected endogenous particles in exhaled breath in subjects with COVID-19 disease by two different impaction-based methods, during 20 normal breaths, 10 airway opening breaths, and three coughs, respectively. Breath samples were analyzed with reverse transcription real-time polymerase chain reaction (RT-PCR).

RESULTS: Detection of RNA in aerosol was possible in 10 out of 25 subjects. Presence of virus RNA in aerosol was mainly found in cough samples (n = 8), but also in airway opening breaths (n = 3) and in normal breaths (n = 4), with no overlap between the methods. No association between viral load in aerosol and number exhaled particles <5 μm was found. Subjects with COVID-19 exhaled less particles than healthy controls during normal breathing and airway opening breaths (all P < 0.05), but not during cough.

CONCLUSION: SARS-CoV-2 RNA can be detected in exhaled aerosol, sampled during a limited number of breathing and coughing procedures. Detection in aerosol seemed independent of viral load in the upper airway swab as well as of the exhaled number of particles. The infectious potential of the amount of virus detected in aerosol needs to be further explored.