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. 2020 Nov 3;17(21):8114.
doi: 10.3390/ijerph17218114.

Model Calculations of Aerosol Transmission and Infection Risk of COVID-19 in Indoor Environments

Jos Lelieveld  1   2 , Frank Helleis  1 , Stephan Borrmann  1 , Yafang Cheng  1 , Frank Drewnick  1 , Gerald Haug  1 , Thomas Klimach  1 , Jean Sciare  1   2 , Hang Su  1 , Ulrich Pöschl  1
Affiliations

Model Calculations of Aerosol Transmission and Infection Risk of COVID-19 in Indoor Environments

Jos Lelieveld et al. Int J Environ Res Public Health. .

Abstract

The role of aerosolized SARS-CoV-2 viruses in airborne transmission of COVID-19 has been debated. The aerosols are transmitted through breathing and vocalization by infectious subjects. Some authors state that this represents the dominant route of spreading, while others dismiss the option. Here we present an adjustable algorithm to estimate the infection risk for different indoor environments, constrained by published data of human aerosol emissions, SARS-CoV-2 viral loads, infective dose and other parameters. We evaluate typical indoor settings such as an office, a classroom, choir practice, and a reception/party. Our results suggest that aerosols from highly infective subjects can effectively transmit COVID-19 in indoor environments. This "highly infective" category represents approximately 20% of the patients who tested positive for SARS-CoV-2. We find that "super infective" subjects, representing the top 5-10% of subjects with a positive test, plus an unknown fraction of less-but still highly infective, high aerosol-emitting subjects-may cause COVID-19 clusters (>10 infections). In general, active room ventilation and the ubiquitous wearing of face masks (i.e., by all subjects) may reduce the individual infection risk by a factor of five to ten, similar to high-volume, high-efficiency particulate air (HEPA) filtering. A particularly effective mitigation measure is the use of high-quality masks, which can drastically reduce the indoor infection risk through aerosols.

Keywords: COVID-19; SARS-CoV-2 virus; aerosol particles; airborne transmission; indoor environment; infection risk.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Individual risk of a particular person being infected (equivalent to the percentage of the group being infected) in four indoor environments and five scenarios, for standard and superspreading conditions. Scenario A: passive ventilation, no masks. Scenario B: active ventilation with outside air, no masks. Scenario C: active ventilation, facial masks (not for choir). Scenario D: active ventilation, high-quality masks (not for choir). Scenario E: high-volume filtration with HEPA.
Figure 2
Figure 2
Individual risk of a particular person being infected (equivalent to the percentage of the group being infected), comparing a party with a reception and a choir practice, for three scenarios. Scenario A: passive ventilation, no masks. Scenario B: active ventilation with outside air, no masks. Scenario E: High-volume filtration with HEPA.
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