A population framework for predicting the proportion of people infected by the far-field airborne transmission of SARS-CoV-2 indoors

Iddon, Christopher; Jones, Benjamin; Sharpe, Patrick; Çevik, Müge; Fitzgerald, Shaun

doi:10.1016/j.buildenv.2022.109309

Cited by 6 publications

(5 citation statements)

References 55 publications

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“…Our data suggest that effects of CO2 exceedance on SARS-CoV-2 incidence may depend on other classroom conditions besides occupancy levels that were different between pre-lockdown and post-lockdown period, and that may determine the dose of SARS-CoV-2 present in inhaled air (for instance difference in physical distance between subjects in class, difference in frequency of infectious subjects being present depending on testing policy). Our findings are in line with those of a modeling study that suggested ventilation has little effect on overall transmission risk [ 21 ]. Their study concluded that ventilation at room level can only have an effect on long range transmission and this requires presence of an infected person in the room with a very high emission rate of virus [ 21 ].…”

Section: Discussionsupporting

confidence: 92%

“…Our findings are in line with those of a modeling study that suggested ventilation has little effect on overall transmission risk [ 21 ]. Their study concluded that ventilation at room level can only have an effect on long range transmission and this requires presence of an infected person in the room with a very high emission rate of virus [ 21 ]. To our knowledge, no other field-studies are available that assessed the association between percent-time CO 2 exceedance and SARS-CoV-2 incidence in secondary schools.…”

Section: Discussionsupporting

confidence: 92%

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SARS-CoV-2 incidence in secondary schools; the role of national and school-initiated COVID-19 measures

et al. 2023

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Introduction Our aim was to gain insight into the effect of COVID-19 measures on SARS-CoV-2 incidence in secondary schools and the association with classroom CO2 concentration and airborne contamination. Methods Between October 2020—June 2021, 18 schools weekly reported SARS-CoV-2 incidence and completed surveys on school-initiated COVID-19 measures (e.g. improving hygiene or minimizing contacts). CO2 was measured in occupied classrooms twice, and SARS-CoV-2 air contamination longitudinally using electrostatic dust collectors (EDC) and analyzed using RT-qPCR. National COVID-19 policy measures varied during pre-lockdown, lockdown and post-lockdown periods. During the entire study, schools were recommended to improve ventilation. SARS-CoV-2 incidence rate ratios (IRR) were estimated by Generalized Estimating Equation (GEE) models. Results During 18 weeks follow-up (range: 10–22) SARS-CoV-2 school-incidence decreased during national lockdown (adjusted IRR: 0.41, 95%CI: 0.21–0.80) and post-lockdown (IRR: 0.60, 0.39–0.93) compared to pre-lockdown. School-initiated COVID-19 measures had no additional effect. Pre-lockdown, IRRs per 10% increase in time CO2 exceeded 400, 550 and 800 ppm above outdoor level respectively, were 1.08 (1.00–1.16), 1.10 (1.02–1.19), and 1.08 (0.95–1.22). Post-lockdown, CO2-concentrations were considerably lower and not associated with SARS-CoV-2 incidence. No SARS-CoV-2 RNA was detected in any of the EDC samples. Conclusion During a period with low SARS-CoV-2 population immunity and increased attention to ventilation, with CO2 levels most of the time below acceptable thresholds, only the national policy during and post-lockdown of reduced class-occupancy, stringent quarantine, and contact testing reduced SARS-CoV-2 incidence in Dutch secondary schools. Widespread SARS-CoV-2 air contamination could not be demonstrated in schools under the prevailing conditions during the study.

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Section: Discussionsupporting

confidence: 92%

Section: Discussionsupporting

confidence: 92%

SARS-CoV-2 incidence in secondary schools; the role of national and school-initiated COVID-19 measures

et al. 2023

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“…Most of the studies were based on retrospective analyses of real-world settings with many factors either left uncontrolled or not measured including; the viral load of the infectors, the number of infectors, the size of the susceptible population, infection risk of the host outside the investigated setting, and the influence of other NPIs etc. [29]. These factors can influence the risk of transmission; for example, the viral emission in aerosols emitted from infected subjects during different respiratory activities such as breathing, talking and singing have been reported to vary between 0 and 10 7 RNA copies per hour and the total volume of aerosols emitted is dependent on respiratory activity [30][31][32][33][34][35][36].…”

Section: Discussionmentioning

confidence: 99%

Non-pharmaceutical interventions for COVID-19: a systematic review on environmental control measures

Madhusudanan,

Iddon,

Cevik

et al. 2023

Phil. Trans. R. Soc. A.

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The purpose of this review was to identify the effectiveness of environmental control (EC) non-pharmaceutical interventions (NPIs) in reducing transmission of SARS-CoV-2 through conducting a systematic review. EC NPIs considered in this review are room ventilation, air filtration/cleaning, room occupancy, surface disinfection, barrier devices, CO 2 monitoring and one-way-systems. Systematic searches of databases from Web of Science, Medline, EMBASE, preprint servers MedRxiv and BioRxiv were conducted in order to identify studies reported between 1 January 2020 and 1 December 2022. All articles reporting on the effectiveness of ventilation, air filtration/cleaning, room occupancy, surface disinfection, barrier devices, CO 2 monitoring and one-way systems in reducing transmission of SARS-CoV-2 were retrieved and screened. In total, 13 971 articles were identified for screening. The initial title and abstract screening identified 1328 articles for full text review. Overall, 19 references provided evidence for the effectiveness of NPIs: 12 reported on ventilation, 4 on air cleaning devices, 5 on surface disinfection, 6 on room occupancy and 1 on screens/barriers. No studies were found that considered the effectiveness of CO 2 monitoring or the implementation of one-way systems. Many of these studies were assessed to have critical risk of bias in at least one domain, largely due to confounding factors that could have affected the measured outcomes. As a result, there is low confidence in the findings. Evidence suggests that EC NPIs of ventilation, air cleaning devices and reduction in room-occupancy may have a role in reducing transmission in certain settings. However, the evidence was usually of low or very low quality and certainty, and hence the level of confidence ascribed to this conclusion is low. Based on the evidence found, it was not possible to draw any specific conclusions regarding the effectiveness of surface disinfection and the use of barrier devices. From these results, we further conclude that community agreed standards for well-designed epidemiological studies with low risk of bias are needed. Implementation of such standards would enable more confident assessment in the future of the effectiveness of EC NPIs in reducing transmission of SARS-CoV-2 and other pathogens in real-world settings. This article is part of the theme issue ‘The effectiveness of non-pharmaceutical interventions on the COVID-19 pandemic: the evidence’.

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Section: Covid-19 Ventilation Guidancementioning

confidence: 99%

“…However, evidence from past outbreaks and modelling work 25 suggested that it is the very poorly ventilated spaces that are at greater risk, and those spaces that are ventilated to current UK building regulation standards pose a much lower risk of transmission and hence it may be more pragmatic to focus on improving those spaces that are at highest risk as the highest priority for interventions. 26,35 Approved Document F 36 of the building regulations and CIBSE 1 Guide A 37 provide a range of suggested airflows for various indoor space types that typically range from 5-10 L/s/person. These values originate from studies on occupant comfort to "stuffiness" (the general release of bioeffluents from occupants), where it has been determined that a high level of comfort in occupied spaces can be delivered with 8 L/s/person and therefore 10 L/s/person has often been chosen as a reasonable figure to provide occupant comfort, whilst balancing the energy requirements to deliver outside air.…”

Section: Covid-19 Ventilation Guidancementioning

confidence: 99%

Measurement and rapid assessment of indoor air quality at mass gathering events to assess ventilation performance and reduce aerosol transmission of SARS-CoV-2

Malki-Epshtein

Adzic

Roberts

et al. 2022

Building Services Engineering Research and Technology

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To assess risk factors for COVID-19 transmission and address the closure of mass gathering events since March 2020, the UK Government ran the Events Research Programme (ERP), following which it reopened live events in sports, music, and culture in July 2021. We report the rapid post-occupancy evaluation of Indoor Air Quality (IAQ) and associated long-range airborne transmission risk conducted in the Environmental Study of the ERP. Ten large venues around the UK were monitored with CO2 sensors at a high spatial and temporal resolution during 90 events. An IAQ Index based on CO2 concentration was developed, and all monitored spaces were classified in bands from A to G based on their average and maximum CO2 concentrations from all events. High resolution monitoring and the IAQ Index depicted the overall state of ventilation at live events, and allowed identification of issues with ventilation effectiveness and distribution, and of spaces with poor ventilation and the settings in which long-range airborne transmission risk may be increased. In numerous settings, CO2 concentrations were found to follow patterns relating to event management and specific occupancy of spaces around the venues. Good ventilation was observed in 90% of spaces monitored for given occupancies. Practical applications: High-resolution monitoring of indoor CO2 concentrations is necessary to detect the spatial variation of indoor air quality (IAQ) in large mass gathering event venues. The paper summarises COVID-19 ventilation guidance for buildings and defines a methodology for measurement and rapid assessment of IAQ during occupancy at live events that can be implemented by venue managers. Comparisons of the CO2 concentrations measured during the events identified the spaces at high risk of long-range transmission of airborne pathogens. Building operators should be mindful of the ventilation strategies used relative to the total occupancy in different spaces and the occupant’s activities.

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A population framework for predicting the proportion of people infected by the far-field airborne transmission of SARS-CoV-2 indoors

Cited by 6 publications

References 55 publications

SARS-CoV-2 incidence in secondary schools; the role of national and school-initiated COVID-19 measures

SARS-CoV-2 incidence in secondary schools; the role of national and school-initiated COVID-19 measures

Non-pharmaceutical interventions for COVID-19: a systematic review on environmental control measures

Measurement and rapid assessment of indoor air quality at mass gathering events to assess ventilation performance and reduce aerosol transmission of SARS-CoV-2

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