Working Paper Article Version 1 This version is not peer-reviewed

Analysis of Two Choir Outbreaks in Germany in 2020 Characterizes Long- range Transmission Risks Through SARS-CoV-2

Version 1 : Received: 17 June 2021 / Approved: 21 June 2021 / Online: 21 June 2021 (14:49:39 CEST)

How to cite: Reichert, F.; Stier, O.; Hartmann, A.; Ruscher, C.; Brinkmann, A.; Grossegesse, M.; Neumann, M.; Werber, D.; Hausner, M.; Kunze, M.; Weiß, B.; Michel, J.; Nitsche, A.; Kriegel, M.; Corman, V.M.; Jones, T.C.; Drosten, C.; Brommann, T.; Buchholz, U. Analysis of Two Choir Outbreaks in Germany in 2020 Characterizes Long- range Transmission Risks Through SARS-CoV-2. Preprints 2021, 2021060518 Reichert, F.; Stier, O.; Hartmann, A.; Ruscher, C.; Brinkmann, A.; Grossegesse, M.; Neumann, M.; Werber, D.; Hausner, M.; Kunze, M.; Weiß, B.; Michel, J.; Nitsche, A.; Kriegel, M.; Corman, V.M.; Jones, T.C.; Drosten, C.; Brommann, T.; Buchholz, U. Analysis of Two Choir Outbreaks in Germany in 2020 Characterizes Long- range Transmission Risks Through SARS-CoV-2. Preprints 2021, 2021060518

Abstract

Background: Superspreading events are important drivers of the SARS-CoV-2 pandemic. By analyzing two outbreaks associated with choir rehearsals in March 2020, we demonstrate the risk of indoor, long-range (LR) transmission and singing, to help prevent similar outbreaks. Methods: We conducted two retrospective cohort studies and obtained demographic, clinical, laboratory and contact data, performed SARS-CoV-2 serology, whole genome sequencing (WGS), calculated LR transmission probabilities, measured particle emissions of selected choir members, and calculated particle air concentrations and inhalation doses.Results: We included 65 (84%) and 42 (100%) members of choirs 1 and 2, respectively. WGS confirmed strain identity in both choirs and the primary case of choir 1 (transmitting presymptomatically). Particle emission rate when singing was 7 times higher compared to talking. In choir 1, the median concentration of primary cases’ emitted particles was 8 times higher, exposure at least 30 minutes longer and room volume smaller than in choir 2, resulting in markedly different estimated probabilities for LR transmission (median: 89% vs. 18%, 95%CI: 80-95% vs. 6-36%). Observed AR in choir 1 (89%) was significantly higher than in choir 2 (24%). According to a risk model, first transmission in choir 1 occurred likely after 7 minutes of singing. The number of inhaled particles emitted by an infectious case, sufficient to infect 50% of exposed, was calculated to 1039-2883 particles (95%CI).Conclusions: Even in large rooms, singing of an infectious person may lead to secondary infections through LR exposure within minutes. Given the potential for presymptomatic infectiousness, greatest caution is required wherever aerosols can accumulate.

Keywords

SARS-CoV-2; Singing; Disease Outbreaks; Aerosols; Dose-Response Model

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