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Quantitative Microbial Risk Assessment for Airborne Transmission of SARS-CoV-2 via Breathing, Speaking, Singing,
Jack Schijven1,2, Lucie C Vermeulen1, Arno Swart1
1Centre for Infectious Disease Control, National Institute for Public Health and the Environment (RIVM), Bilthoven, Netherlands.
Background:
Evidence for indoor airborne transmission of SARS-CoV-2 is accumulating.
Objectives:
We assessed of the risk of illness due to airborne SARS-CoV-2 particles from breathing, speaking, singing, coughing, and sneezing in indoor environments.
Methods:
A risk assessment model, AirCoV2, for exposure to SARS-CoV-2 particles in aerosol droplets was developed. Previously published data on droplets expelled by breathing, speaking, singing, coughing, and sneezing by an infected person were used as inputs. Scenarios encompassed virus concentration, exposure time, and ventilation. Newly collected data of virus RNA copies in mucus from patients are presented.
Results:
The expelled volume of aerosols was highest for a sneeze, followed by a cough, singing, speaking, and breathing. After 20 min of exposure, at RNA copies/mL in mucus, all mean illness risks were largely estimated to be below 0.001, except for the "high" sneeze scenario. At virus concentrations above RNA copies/mL, and after 2 h of exposure, in the high and "low" sneeze scenarios, the high cough scenario and the singing scenario, risks exceeded 0.01 and may become very high, whereas the low coughing scenario, the high and low speaking scenarios and the breathing scenario remained below 0.1. After 2 h of exposure, singing became the second highest risk scenario. One air exchange per hour reduced risk of illness by about a factor of 2. Six air exchanges per hour reduced risks of illness by a factor of 8-13 for the sneeze and cough scenarios and by a factor of 4-9 for the other scenarios.
Discussion:
The large variation in the volume of expelled aerosols is discussed. The model calculations indicated that SARS-CoV-2 transmission via aerosols outside of the social distancing norm can occur. Virus concentrations in aerosols and/or the amount of expelled aerosol droplets need to be high for substantial transmission via this route. AirCoV2 is made available as interactive computational tool. https://doi.org/10.1289/EHP7886.
Insights
Airborne SARS-CoV-2 transmission is a significant risk indoors. High virus concentrations and prolonged exposure, especially from sneezing or singing, increase illness risk, but ventilation can substantially reduce it.
Area of Science:
- Environmental health
- Infectious disease transmission
- Aerosol science
Background:
- Accumulating evidence suggests SARS-CoV-2 can transmit indoors via airborne particles.
- Understanding the risk associated with different human activities is crucial for public health interventions.
Purpose of the Study:
- To assess the risk of SARS-CoV-2 infection from airborne particles generated by various activities (breathing, speaking, singing, coughing, sneezing) in indoor settings.
- To develop and utilize a risk assessment model, AirCoV2, to quantify these risks under different exposure scenarios.
Main Methods:
- Developed the AirCoV2 risk assessment model for SARS-CoV-2 aerosol exposure.
- Incorporated published data on droplet expulsion from various activities and new data on virus RNA concentrations in patient mucus.
- Simulated scenarios with varying virus concentration, exposure time, and ventilation rates (air changes per hour).
Main Results:
- Aerosol expulsion volume was highest for sneezing, followed by coughing and singing.
- Illness risks were generally low (<0.001) after 20 minutes at low virus concentrations, except for high sneeze scenarios.
- After 2 hours, high virus concentrations elevated risks significantly for sneezing, coughing, and singing, with ventilation reducing risk by factors of 2 to 13.
Conclusions:
- SARS-CoV-2 can transmit via aerosols even outside standard social distancing norms, particularly with high virus loads and prolonged exposure.
- Singing poses a significant airborne transmission risk, second only to sneezing under certain conditions.
- Effective ventilation is critical for mitigating airborne SARS-CoV-2 transmission risk in indoor environments.
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