Practical Indicators for Risk of Airborne Transmission in Shared Indoor Environments and Their Application to COVID-19 Outbreaks

Peng, Z.; Rojas, A.L. Pineda; Kropff, E.; Bahnfleth, W.; Buonanno, G.; Dancer, S.J.; Kurnitski, J.; Li, Y.; Loomans, M.G.L.C.; Marr, L.C.; Morawska, L.; Nazaroff, W.; Noakes, C.; Querol, X.; Sekhar, C.; Tellier, R.; Greenhalgh, T.; Bourouiba, L.; Boerstra, A.; Tang, J.W.; Miller, S.L.; Jimenez, J.L.

Abstract

Some infectious diseases, including COVID-19, can undergo airborne transmission. This may happen at close proximity, but as time indoors increases, infections can occur in shared room air despite distancing. We propose two indicators of infection risk for this situation, that is, relative risk parameter (Hr) and risk parameter (H). They combine the key factors that control airborne disease transmission indoors: virus-containing aerosol generation rate, breathing flow rate, masking and its quality, ventilation and aerosol-removal rates, number of occupants, and duration of exposure. COVID-19 outbreaks show a clear trend that is consistent with airborne infection and enable recommendations to minimize transmission risk. Transmission in typical prepandemic indoor spaces is highly sensitive to mitigation efforts. Previous outbreaks of measles, influenza, and tuberculosis were also assessed. Measles outbreaks occur at much lower risk parameter values than COVID-19, while tuberculosis outbreaks are observed at higher risk parameter values. Because both diseases are accepted as airborne, the fact that COVID-19 is less contagious than measles does not rule out airborne transmission. It is important that future outbreak reports include information on masking, ventilation and aerosol-removal rates, number of occupants, and duration of exposure, to investigate airborne transmission.

• Journal Article Type: Article
• Acceptance Date: Dec 13, 2021
• Online Publication Date: Jan 5, 2022
• Publication Date: Jan 18, 2022
• Deposit Date: Feb 11, 2022
• Publicly Available Date: Feb 11, 2022
• Journal: Environmental Science & Technology
• Print ISSN: 0013-936X
• Electronic ISSN: 1520-5851
• Publisher: American Chemical Society
• Peer Reviewed: Peer Reviewed
• Volume: 56
• Issue: 2
• Pages: 1125-1137
• DOI: https://doi.org/10.1021/acs.est.1c06531
• Keywords: COVID-19, airborne transmission, outbreaks, indoor air, risk assessment, mitigation
• Public URL: http://researchrepository.napier.ac.uk/Output/2844807