Is there an airborne component to the transmission of COVID-19? : a quantitative analysis study
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Abstract
Objectives
While COVID-19 is known to be spread by respiratory droplets (which travel <2m horizontally), much less is known about its transmission via aerosols, which can become airborne and widely distributed throughout room spaces. In order to quantify the risk posed by COVID-19 infectors exhaling respiratory aerosols in enclosed spaces, we undertook a computer modelling study to simulate transmission in an office building.
Methods
Respiratory droplet data from four published datasets were analysed to quantify the number and volume of droplets <100μm diameter produced by a typical cough and speaking event (i.e. counting from 1 to 100). This was used in a stochastic model to simulate (10000 simulations) the number of respiratory particles, originating from a COVID-19 infector, that would be inhaled in one hour by a susceptible individual practicing socially distancing in a 4 × 4 × 2.5m office space. Several scenarios were simulated that mimicked the presence of both symptomatic and asymptomatic COVID-19 infectors.
Results
On average, each cough and speaking event produced similar numbers of droplets <100μm diameter (median range = 971.9 – 1013.4). Computer simulations (ventilation rate=2AC/h) revealed that sharing the office space with a symptomatic COVID-19 infector (4 coughs and 10 speaking events per hour) for one hour resulted in the inhalation of 16.9 (25-75 th range = 8.1-33.9) aerosolised respiratory droplets, equating to about 280-1190 particles inhaled over a 35-hour working week. Sharing with an asymptomatic infector (10 speaking events per hour) resulted in the about 196–875 particles inhaled over 35 hours.
Conclusions
Given that live SARS-CoV-2 virions are known to be shed in high concentrations from the nasal cavity of both symptomatic and asymptomatic COVID-19 patients, the results suggest that those sharing enclosed spaces with infectors for long periods may be at risk of contracting COVID-19 by the aerosol route, even when practicing social distancing.
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SciScore for 10.1101/2020.05.22.20109991: (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, notwithstanding these limitations, the results imply that if someone with COVID-19 is present in an enclosed space, others in that space may be at risk of inhaling aerosol particles containing SARS-CoV-2 virions, even when social distancing is practiced. As such, this supports the findings of other studies that suggest that the …
SciScore for 10.1101/2020.05.22.20109991: (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, notwithstanding these limitations, the results imply that if someone with COVID-19 is present in an enclosed space, others in that space may be at risk of inhaling aerosol particles containing SARS-CoV-2 virions, even when social distancing is practiced. As such, this supports the findings of other studies that suggest that the airborne transmission of COVID-19 might be taking place [3, 6]. Of course, the inhalation of respiratory droplets and droplet nuclei exhaled from COVID-19 positive individuals does not necessarily mean that any infection will be transmitted. This is because the particles inhaled may not contain any SARS-CoV-2 virions, or alternatively, the dose received may be below the threshold necessary to cause an infection in a susceptible individual. Also, the host’s immunological status might mean that they are less susceptible to acquiring a COVID-19 infection. While the minimum infectious dose necessary to cause a COVID-19 infection is not known, the ID10 and ID50 values (i.e. the doses required to cause infection in 10% and 50% of people) for SARS-CoV-1 (the causative agent in SARS) have been estimated to be 43 and 280 PFU respectively [37]. Therefore, if the infectivity of SARS-CoV-2 is similar to that of SARS-CoV-1, this implies that inhalation of just a few hundred virions might be enough to infect 50% of those exposed to COVID-19. Furthermore, it has been shown recently that the average virus RNA load in the sputum of hospitalised COVID-19 patien...
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.
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