Estimation of SARS-CoV-2 aerosol emissions from simulated patients with COVID-19 and no to moderate symptoms
Abstract
Importance
Cases of the coronavirus disease 2019 (COVID-19) with no or mild symptoms were reported to frequently transmit the disease even without direct contact. The severe acute respiratory syndrome virus (SARS-COV-2) was found at very high concentrations in swab and sputum of such cases.
Objective
We aimed to estimate in a mathematical modeling study the virus release from such cases into different aerosol sizes by normal breathing and coughing, and what exposure can result from this in a room shared with such as case.
Data Sources and Model
We combined the size-distribution of exhaled breath microdroplets for coughing and normal breathing with viral sputum concentrations as approximation for lung lining liquid to obtain an estimate of emitted virus levels. The resulting emission data fed a single-compartment model of airborne concentrations in a room of 50 m3, the size of a small office or medical exam room.
Results
The estimated viral load in microdroplets emitted by simulated patients while breathing normally was on typical 0.0000049 copies/cm3 and could go up to 0.637 copies/cm3. The corresponding numbers for coughing simulated patients were 0.277 copies/cm3 and 36,030/cm3, respectively, per cough. The resulting concentrations in a room with a coughing emitter were always very high, up to 7.44 million copies/m3. However, also regular breathing microdroplets from high emitters was modelled to lead to 1248 copies/m3.
Conclusions and Relevance
In this modelling study, breathing and coughing were estimated to release large numbers of viruses, ranging from thousands to millions of virus copies/m3 in a room with an emitter having a high viral load, depending on ventilation and microdroplet formation process. These findings suggest that strict respiratory protection may be needed when there is a chance to be in the same room with a patient - whether symptomatic or not - especially for a prolonged time.
Key Points
Question
How much SARS-CoV-2 virus is released from a case by breathing and coughing, and what is the resulting concentration in a room?
Finding
In this mathematical modelling study, both, breathing and coughing were estimated to release large numbers of viruses, which can lead to millions of virus copies/m3 in a poorly ventilated room with a coughing emitter.
Meaning
These results may explain the important rate of transmissions and implies the need for strict respiratory protection when people are in the same room with a case with COVID-19.
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