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Meta-Analysis
. 2024 Oct 16;230(4):e824-e836.
doi: 10.1093/infdis/jiae261.

The Risk of SARS-CoV-2 Transmission in Community Indoor Settings: A Systematic Review and Meta-analysis

Mark Rohit Francis  1 , Saheed Gidado  1 , J Pekka Nuorti  1   2
Affiliations
Meta-Analysis

The Risk of SARS-CoV-2 Transmission in Community Indoor Settings: A Systematic Review and Meta-analysis

Mark Rohit Francis et al. J Infect Dis. .

Abstract

Background: Quantifying the risk of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) transmission in indoor settings is crucial for developing effective non-vaccine prevention strategies and policies. However, summary evidence on the transmission risks in settings other than households, schools, elderly care, and health care facilities is limited. We conducted a systematic review to estimate the secondary attack rates (SARs) of SARS-CoV-2 and the factors modifying transmission risk in community indoor settings.

Methods: We searched Medline, Scopus, Web of Science, WHO COVID-19 Research Database, MedrXiv, and BiorXiv from 1 January 2020 to 20 February 2023. We included articles with original data for estimating SARS-CoV-2 SARs. We estimated the overall and setting-specific SARs using the inverse variance method for random-effects meta-analyses.

Results: We included 34 studies with data on 577 index cases, 898 secondary cases, and 9173 contacts. The pooled SAR for community indoor settings was 20.4% (95% confidence interval [CI], 12.0%-32.5%). The setting-specific SARs were highest for singing events (SAR, 44.9%; 95% CI, 14.5%-79.7%), indoor meetings and entertainment venues (SAR, 31.9%; 95% CI, 10.4%-65.3%), and fitness centers (SAR, 28.9%; 95% CI, 9.9%-60.1%). We found no difference in SARs by index case, viral, and setting-specific characteristics.

Conclusions: The risk of SARS-CoV-2 transmission was highest in indoor settings where singing and exercising occurred. Effective mitigation measures such as assessing and improving ventilation should be considered to reduce the risk of transmission in high-risk settings. Future studies should systematically assess and report the host, viral, and setting-specific characteristics that may modify the transmission risks of SARS-CoV-2 and other respiratory viruses in indoor environments.

Keywords: COVID-19; SARS-CoV-2; community settings; indoors; secondary attack rate; transmission.

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Conflict of interest statement

Potential conflicts of interest All authors: No reported conflicts of interest. All authors have submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Conflicts that the editors consider relevant to the content of the manuscript have been disclosed.

Figures

Figure 1.
Figure 1.
Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) flow diagram for study selection.
Figure 2.
Figure 2.
Forest plot for the overall and setting-specific secondary attack rates. Study-level estimates and exact binomial 95% CIs are shown along with the pooled summary SARs by setting category and across studies. The studies are arranged in ascending order of the magnitude of the study-level estimates within each setting category. Abbreviations: CI, confidence interval; SAR, secondary attack rate.
Figure 3.
Figure 3.
Funnel plot of study size (total contacts) versus logit transformed SARs to assess publication bias in the included studies, as recommended by Hunter et al (2014) [21]. Abbreviation: SAR, secondary attack rate.
See this image and copyright information in PMC

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References

    1. World Health Organization . WHO COVID-19 dashboard. https://data.who.int/dashboards/covid19/cases. Accessed 28 December 2023.
    1. Fung HF, Martinez L, Alarid-Escudero F, et al. . The household secondary attack rate of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2): a rapid review. Clin Infect Dis 2021; 73:S138–45. - PMC - PubMed
    1. Madewell Z, Yang Y, Longini I, Halloran M, Dean N. Household transmission of SARS-CoV-2 a systematic review and meta-analysis. JAMA Netw Open 2020; 3:e2031756. - PMC - PubMed
    1. Leclerc QJ, Fuller NM, Knight LE; CMMID COVID-19 Working Group, Funk S, Knight GM. What settings have been linked to SARS-CoV-2 transmission clusters? Wellcome Open Res 2020; 5:83. - PMC - PubMed
    1. Thompson HA, Mousa A, Dighe A, et al. . Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) setting-specific transmission rates: a systematic review and meta-analysis. Clin Infect Dis 2021; 73:e754–64. - PMC - PubMed