SARS-CoV-2 Aerosol Transmission Indoors: A Closer Look at Viral Load, Infectivity, the Effectiveness of Preventive Measures and a Simple Approach for Practical Recommendations
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Abstract
There is uncertainty about the viral loads of infectious individuals required to transmit COVID-19 via aerosol. In addition, there is a lack of both quantification of the influencing parameters on airborne transmission and simple-to-use models for assessing the risk of infection in practice, which furthermore quantify the influence of non-medical preventive measures. In this study, a dose–response model was adopted to analyze 25 documented outbreaks at infection rates of 4–100%. We show that infection was only possible if the viral load was higher than 108 viral copies/mL. Based on mathematical simplifications of our approach to predict the probable situational attack rate (PARs) of a group of persons in a room, and valid assumptions, we provide simplified equations to calculate, among others, the maximum possible number of persons and the person-related virus-free air supply flow necessary to keep the number of newly infected persons to less than one. A comparison of different preventive measures revealed that testing contributes the most to the joint protective effect, besides wearing masks and increasing ventilation. In addition, we conclude that absolute volume flow rate or person-related volume flow rate are more intuitive parameters for evaluating ventilation for infection prevention than air exchange rate.
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SciScore for 10.1101/2021.11.04.21265910: (What is this?)
Please note, not all rigor criteria are appropriate for all manuscripts.
Table 1: Rigor
NIH rigor criteria are not applicable to paper type.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:However, different limitations as well regarding the model as the practical application have to be considered. First of all, different influencing factors (e.g. critical dose, decay rate of sedimentation as well as inactivation, size distribution and number of emitted particles) were assumed based on current knowledge, but whereas the …
SciScore for 10.1101/2021.11.04.21265910: (What is this?)
Please note, not all rigor criteria are appropriate for all manuscripts.
Table 1: Rigor
NIH rigor criteria are not applicable to paper type.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:However, different limitations as well regarding the model as the practical application have to be considered. First of all, different influencing factors (e.g. critical dose, decay rate of sedimentation as well as inactivation, size distribution and number of emitted particles) were assumed based on current knowledge, but whereas the transmission of SARS-CoV-2 is still ongoing, further knowledge may be gained from further research. The decay rates of sedimentation as well as inactivation can be influenced by the particle size distribution as well as the air temperature and humidity in the room. Furthermore, the analysis and model base on some general assumptions like ideal mixing of all particles within the room, an initial concentration of 0 virus copies/m3 and a supply of virus free air. An ideal mixing of all particles in the room also implies, that no separation into near and far field can be performed, whereas the concentration of virus laden particles near the person is probably higher than in the rest of the room. Also, the local concentration will differ regularly from the average concentration so that the local air quality index should be considered for investigations in detail [27, 28]. As a result, even at lower viral emission rate Sv, infection can occur via aerosol, predominantly in the near field. As a third aspect the influence of VOCs is difficult to define. A higher transmission rate of new VOCs may result from different aspects, such as a change in critical...
Results from TrialIdentifier: No clinical trial numbers were referenced.
Results from Barzooka: We found bar graphs of continuous data. We recommend replacing bar graphs with more informative graphics, as many different datasets can lead to the same bar graph. The actual data may suggest different conclusions from the summary statistics. For more information, please see Weissgerber et al (2015).
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.
Results from scite Reference Check: We found no unreliable references.
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