High SARS-CoV-2 attack rates following exposure during five singing events in the Netherlands, September-October 2020

  1. Anita A. Shah
  2. Florien Dusseldorp
  3. Irene K. Veldhuijzen
  4. Margreet J.M. te Wierik
  5. Alvin Bartels
  6. Jack Schijven
  7. Lucie C. Vermeulen
  8. Mirjam J. Knol

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Abstract

Background

Previous reports suggest SARS-CoV-2 transmission risk increases during singing events. From September-October 2020, several clusters of COVID-19 cases among singing events were reported across the Netherlands. Our aim was to investigate whether singing increased SARS-CoV-2 transmission risk during these events.

Methods

Data from 5 events were retrospectively collected from spokespersons and singing group members via questionnaires. Information was consolidated with the National Notifiable Diseases Surveillance System. Specimens were requested for sequencing for point source and cluster assessment. We described outbreaks in terms of person, place and time and depicted potential SARS-CoV-2 transmission routes. A previously published model (AirCoV2) was used to estimate mean illness risk of 1 person through airborne transmission under various scenarios.

Results

Events included 9-21 persons (mean: 16), aged 20-89 years (median: 62). Response rates ranged 58-100%. Attack rates were 53-74%. Limited sequencing data was obtained from 2 events. Events lasted 60-150 minutes (singing: 20-120). Rooms ranged 320-3000m 3 . SARS-CoV-2 transmission likely occurred during all events; with a possible index case identified in 4 events. AirCoV2 showed 86% (54-100%) mean illness risk for 120 minutes of singing, smaller room (300m 3 ), 1 air exchange/hour (ACH), and supershedder presence.

Conclusions

Droplet transmission and indirect contact probably caused some cases, but unlikely explain the high attack rates. AirCoV2 indicated that airborne transmission due to singing is possible in case of supershedder presence. Airflow expelling respiratory droplets >1.5m possibly influenced transmission. It is possible that singing itself increased SARS-CoV-2 transmission risk through airborne transmission.

Summary

This outbreak investigation among five singing events with high SARS-CoV-2 attack rates (53-74%) suggested that airflow expelling respiratory droplets >1.5m possibly influenced transmission and it is possible that singing itself increased SARS-CoV-2 transmission risk through airborne transmission.

Article activity feed

  1. Version published to 10.1101/2021.03.30.21253126v2 on medRxiv
  2. ScreenIT

    SciScore for 10.1101/2021.03.30.21253126: (What is this?)

    Please note, not all rigor criteria are appropriate for all manuscripts.

    Table 1: Rigor

    Institutional Review Board StatementConsent: Participation in the questionnaire was voluntary and online informed consent was obtained.
    Randomizationnot detected.
    Blindingnot detected.
    Power Analysisnot detected.
    Sex as a biological variablenot detected.

    Table 2: Resources

    No key resources detected.

    Results from OddPub: We did not detect open data. We also did not detect open code. Researchers are encouraged to share open data when possible (see Nature blog).

    Results from LimitationRecognizer: We detected the following sentences addressing limitations in the study:
    Strengths and limitations: Our study has several strengths; this is the first outbreak investigation which investigates COVID- 19 clusters in several singing groups worldwide. Second, the overall high response rate provided a good indication of the circumstances in which the singing events took place. Third, the questionnaire included questions aimed at identifying direct, indirect and airborne transmission routes. A limitation of this study is the low number of specimens on which we could perform phylogenetic analysis due to limited specimen storage time (usually one week) during the period of the outbreak investigation. Also, a large number of laboratories were involved coupled with a high work load for the public health services. Additionally, asymptomatic cases may have been missed as not all persons were tested. Therefore, we could not identify the number of possible source cases present at the events and/or confirming that the singing group members were infected by a common source. Thirdly, the exact circumstances regarding airflow direction for each of the events was not known, and could not be accounted for in the model. It was also dependent on the weather of that day for the events using natural ventilation. Lastly, due to the retrospective nature of the questionnaires, recall bias could have affected the responses of the participants which indicated the likeliness of dropet or indirect contact transmission. However, almost all singing group members did describe sim...

    Results from TrialIdentifier: No clinical trial numbers were referenced.

    Results from Barzooka: We did not find any issues relating to the usage of bar graphs.

    Results from JetFighter: We did not find any issues relating to colormaps.

    Results from rtransparent:
    • Thank you for including a conflict of interest statement. Authors are encouraged to include this statement when submitting to a journal.
    • Thank you for including a funding statement. Authors are encouraged to include this statement when submitting to a journal.
    • No protocol registration statement was detected.

    About SciScore

    SciScore is an automated tool that is designed to assist expert reviewers by finding and presenting formulaic information scattered throughout a paper in a standard, easy to digest format. SciScore checks for the presence and correctness of RRIDs (research resource identifiers), and for rigor criteria such as sex and investigator blinding. For details on the theoretical underpinning of rigor criteria and the tools shown here, including references cited, please follow this link.

  3. Version published to 10.1101/2021.03.30.21253126v1 on medRxiv