Respiratory virus shedding in exhaled breath and efficacy of face masks
Citation: Nancy H. L. Leung, Daniel K. W. Chu, Eunice Y. C. Shiu, Kwok-Hung Chan, James J. McDevitt, Benien J. P. Hau, Hui-Ling Yen, Yuguo Li, Dennis K. M. Ip, J. S. Malik Peiris, Wing-Hong Seto, Gabriel M. Leung, Donald K. Milton, Benjamin J. Cowling (2020) Respiratory virus shedding in exhaled breath and efficacy of face masks.
Screened 3363 from outpatient clinic in Hong Kong, individuals reporting ≥2 ARI symptoms (fever ≥37.8 °C, cough, sore throat, runny nose, headache, myalgia and phlegm), within 3 d of illness onset and ≥11 years of age were eligible to participate, ultimately enrolling 246 participants who were randomized into mask wearing and not mask wearing groups. Infections were confirmed with RT-PCR of (seasonal) coronavirus (n = 17), influenza virus (n = 43), or rhinovirus (n = 54). Participant breaths were collected for 30 minutes.
Found that masks resulted in significant reduced detection of aerosols and droplets for coronavirus, droplets for influenza, and neither for rhinovirus.
Even without a face mask, some participants did not shed detectable virus in respiratory droplets or aerosols: detected rhinovirus in aerosols in 19 of 34 (56%) participants, 4 of 10 (40%) for influenza, and 8 of 23 (35%) for coronavirus, possibly implying that prolonged close contact would be required for transmission to occur or that there is considerable heterogeneity in infectiousness.