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Transmission of SARS‐CoV‐2 by inhalation of respiratory aerosol in the Skagit Valley Chorale superspreading event

Miller, Shelly L.; Nazaroff, William W.; Jimenez, Jose L.; Boerstra, Atze; Buonanno, Giorgio; Dancer, Stephanie J.; Kurnitski, Jarek; Marr, Linsey C.; Morawska, Lidia; Noakes, Catherine

Authors

Shelly L. Miller

William W. Nazaroff

Jose L. Jimenez

Atze Boerstra

Giorgio Buonanno

Jarek Kurnitski

Linsey C. Marr

Lidia Morawska

Catherine Noakes



Abstract

During the 2020 COVID‐19 pandemic, an outbreak occurred following attendance of a symptomatic index case at a weekly rehearsal on 10 March of the Skagit Valley Chorale (SVC). After that rehearsal, 53 members of the SVC among 61 in attendance were confirmed or strongly suspected to have contracted COVID‐19 and two died. Transmission by the aerosol route is likely; it appears unlikely that either fomite or ballistic droplet transmission could explain a substantial fraction of the cases. It is vital to identify features of cases such as this to better understand the factors that promote superspreading events. Based on a conditional assumption that transmission during this outbreak was dominated by inhalation of respiratory aerosol generated by one index case, we use the available evidence to infer the emission rate of aerosol infectious quanta. We explore how the risk of infection would vary with several influential factors: ventilation rate, duration of event, and deposition onto surfaces. The results indicate a best‐estimate emission rate of 970 ± 390 quanta/h. Infection risk would be reduced by a factor of two by increasing the aerosol loss rate to 5 h−1 and shortening the event duration from 2.5 to 1 h.

Citation

Miller, S. L., Nazaroff, W. W., Jimenez, J. L., Boerstra, A., Buonanno, G., Dancer, S. J., Kurnitski, J., Marr, L. C., Morawska, L., & Noakes, C. (2021). Transmission of SARS‐CoV‐2 by inhalation of respiratory aerosol in the Skagit Valley Chorale superspreading event. Indoor Air, 31(2), 314-323. https://doi.org/10.1111/ina.12751

Journal Article Type Article
Acceptance Date Sep 15, 2020
Online Publication Date Oct 13, 2020
Publication Date 2021-03
Deposit Date Nov 16, 2020
Publicly Available Date Nov 20, 2020
Journal Indoor Air
Print ISSN 0905-6947
Electronic ISSN 1600-0668
Publisher Wiley
Peer Reviewed Peer Reviewed
Volume 31
Issue 2
Pages 314-323
DOI https://doi.org/10.1111/ina.12751
Keywords aerosol transmission, Covid-19, infectious disease, pandemic, risk, ventilation, virus
Public URL http://researchrepository.napier.ac.uk/Output/2698924

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Transmission Of SARS‐CoV‐2 By Inhalation Of Respiratory Aerosol In The Skagit Valley Chorale Superspreading Event (accepted version) (546 Kb)
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Transmission Of SARS‐CoV‐2 By Inhalation Of Respiratory Aerosol In The Skagit Valley Chorale Superspreading Event (submitted version) (253 Kb)
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