Viral Load of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) in Respiratory Aerosols Emitted by Patients With Coronavirus Disease 2019 (COVID-19) While Breathing, Talking, and Singing

Abstract

Background Multiple SARS-CoV-2 superspreading events suggest that aerosols play an important role in driving the COVID-19 pandemic. To better understand how airborne SARS-CoV-2 transmission occurs, we sought to determine viral loads within coarse (>5μm) and fine (≤5μm) respiratory aerosols produced when breathing, talking, and singing. Methods Using a G-II exhaled breath collector, we measured viral RNA in coarse and fine respiratory aerosols emitted by COVID-19 patients during 30 minutes of breathing, 15 minutes of talking, and 15 minutes of singing. Results Thirteen participants (59%) emitted detectable levels of SARS-CoV-2 RNA in respiratory aerosols, including 3 asymptomatic and 1 presymptomatic patient. Viral loads ranged from 63–5,821 N gene copies per expiratory activity per participant, with high person-to-person variation. Patients earlier in illness were more likely to emit detectable RNA. Two participants, sampled on day 3 of illness, accounted for 52% of the total viral load. Overall, 94% of SARS-CoV-2 RNA copies were emitted by talking and singing. Interestingly, 7 participants emitted more virus from talking than singing. Overall, fine aerosols constituted 85% of the viral load detected in our study. Virus cultures were negative. Conclusions Fine aerosols produced by talking and singing contain more SARS-CoV-2 copies than coarse aerosols and may play a significant role in SARS-CoV-2 transmission. Exposure to fine aerosols, especially indoors, should be mitigated. Isolating viable SARS-CoV-2 from respiratory aerosol samples remains challenging, and whether this can be more easily accomplished for emerging SARS-CoV-2 variants is an urgent enquiry necessitating larger-scale studies.

A population framework for predicting the proportion of people infected by the far-field airborne transmission of SARS-CoV-2 indoors

“…Coleman et al . also show that the variability in the amount of genomic material measured in expirated aerosols is consistent with the variability of viral loads determined using swabs and saliva [43].…”

“…Coleman et al . [43] show that SARS-CoV-2 genomic material is detectable in expirated aerosols from some COVID-19 patients, but not all of them because 41% exhaled no detectable genomic material. Singing and talking generally produce more genomic material than breathing, but there is large variability between patients.…”

Pre-adolescent children exhibit lower aerosol particle volume emissions than adults for breathing, speaking, singing and shouting

“…However, generalizing conclusions from age comparisons should be drawn very carefully, recognizing the high person-to-person variability in emitted particles and viral loads in the case of an infection [ 14 ]. It should be emphasized that we determined data for individuals not infected with SARS-CoV-2.…”

Modelling airborne transmission of SARS-CoV-2 using CARA: Risk assessment for enclosed spaces

“…To assess the accuracy of the model, the viral emission rate vR total was benchmarked against experimental data and tuned to the datasets for SARS-CoV-2 [64,82,83] (Supplementary Fig. S.9), with a particle concentration of 0.06 and 0.2 cm -3 for the B and L modes, respectively.…”

“…6,7 in [33]). As for the virological aspects, the published data available is scarce [64,82,83], although the results of the model were still compared to studies using an human source bioaerosol sampler capable of reproducing the wanted measurements (Supplementary Fig. S.9).…”