Effectiveness of public health measures to prevent the transmission of SARS-CoV-2 at mass gatherings: A rapid review.

Mass gatherings play an important role in society, but since the onset of the Covid-19 pandemic, they have generally been restricted in order to mitigate transmission of SARS-CoV-2. The aim of this study was to summarise the evidence regarding the effectiveness of public health measures at preventing the transmission of SARS-CoV-2 at mass gatherings, and hence inform guidance on the organisation of these events. A rapid review was undertaken in Cochrane, Embase (OVID), Medline (OVID), Google, Web of Science and Europe PMC from 1 January 2020 to 3 June 2021. Of the identified 1,624 citations, 14 articles referring to 11 unique studies were included. This rapid review found evidence from 11 studies (involving approximately 30,482 participants) that implementing a range of measures may reduce the risk of SARS-CoV-2 transmission at mass gatherings; however, it is unlikely that this risk can be eliminated entirely. All studies adopted a layered mitigation approach involving multiple measures, which may be more effective than relying on any single measure. The number and intensity of measures implemented varied across studies, with most implementing resource intense measures. Importantly, all included studies were only of 'fair' to 'poor' quality. In conclusion, there is currently limited evidence on the effectiveness of measures to prevent SARS-CoV-2 transmission at mass gatherings. As mass gatherings recommence, continued adoption of known mitigation measures is required to limit the risk of transmission, as well as ongoing research and surveillance to monitor the potential impact of these events on the wider population and healthcare system.

Airborne transmission of SARS-CoV-2 via aerosols.

A key consideration in the Covid-19 pandemic is the dominant modes of transmission of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus. The objective of this review was to synthesise the evidence for the potential airborne transmission of SARS-CoV-2 via aerosols. Systematic literature searches were conducted in PubMed, Embase, Europe PMC and National Health Service UK evidence up to 27 July 2020. A protocol was published and Cochrane guidance for rapid review methodology was adhered to throughout. Twenty-eight studies were identified. Seven out of eight epidemiological studies suggest aerosol transmission may occur, with enclosed environments and poor ventilation noted as possible contextual factors. Ten of the 16 air sampling studies detected SARS-CoV-2 ribonucleic acid; however, only three of these studies attempted to culture the virus with one being successful in a limited number of samples. Two of four virological studies using artificially generated aerosols indicated that SARS-CoV-2 is viable in aerosols. The results of this review indicate there is inconclusive evidence regarding the viability and infectivity of SARS-CoV-2 in aerosols. Epidemiological studies suggest possible transmission, with contextual factors noted. Viral particles have been detected in air sampling studies with some evidence of clinical infectivity, and virological studies indicate these particles may represent live virus, adding further plausibility. However, there is uncertainty as to the nature and impact of aerosol transmission of SARS-CoV-2, and its relative contribution to the Covid-19 pandemic compared with other modes of transmission.