Probable Aerosol Transmission of SARS-CoV-2 through Floors and Walls of Quarantine Hotel, Taiwan, 2021

Effect of Face Mask on Lowering COVID-19 Incidence in School Settings: A Systematic Review

BACKGROUND

The emergence of COVID-19 resulted in a substantial loss of education because of global school closures. Face masks are a potential measure to restrain the COVID-19 spread; therefore, this paper evaluated the effectiveness of face masks in reducing COVID-19 incidence in school settings.

METHODS

A systematic review was conducted by searching the literature in the Cochrane COVID-19 Study Register and the World Health Organization COVID-19 global literature. Data were summarized in tabular forms, and the findings were presented as narrative synthesis.

RESULTS

A total of 15,709 records were retrieved. The screening and selection led to the inclusion of 12 observational and 2 quasi-experimental studies. Nine studies were conducted in different states, counties, or districts of the United States, and the remaining 5 were reported from Germany, Finland, Spain, and the United Kingdom. The results of 10 out of 14 studies favored mask use in reducing school COVID-19 incidence. Three studies found no link between mask use and COVID-19 incidences, whereas 1 quasi-experimental study noted a higher COVID-19 incidence with mask use in students aged 6-11 years than no use of mask among preschool children aged 3-5 years.

CONCLUSION

Mask mandates may lessen the incidence of respiratory infectious diseases in school settings during a pandemic; more well-designed studies are warranted to clarify further the evidence regarding mask use in school settings.

COVID-19 outbreak at a residential apartment building in Northern Ontario, Canada

In February 2021, a cluster of Beta variant (B.1.351) coronavirus disease 2019 (COVID-19) cases were identified in an apartment building located in Northern Ontario, Canada. Most cases had no known contact with each other. Objectives of this multi-component outbreak investigation were to better understand the social and environmental factors that facilitated the transmission of COVID-19 through this multi-unit residential building (MURB). A case-control study examined building-specific exposures and resident behaviours that may have increased the odds of being a case. A professional engineer assessed the building's heating, ventilation, and air-conditioning (HVAC) systems. Whole-genome sequencing and an in-depth genomic analysis were performed. Forty-five outbreak-confirmed cases were identified. From the case-control study, being on the upper floors (OR: 10.4; 95% CI: 1.63-66.9) and within three adjacent vertical lines (OR: 28.3; 3.57-225) were both significantly associated with being a case of COVID-19, after adjusting for age. There were no significant differences in reported behaviours, use of shared spaces, or precautions taken between cases and controls. An assessment of the building's ventilation found uncontrolled air leakage between apartment units. A single genomic cluster was identified, where most sequences were identical to one another. Findings from the multiple components of this investigation are suggestive of aerosol transmission between units.

Investigation of a COVID-19 cluster involving vertical transmission in a residential building, Taiwan, 2021

We investigated a COVID-19 cluster involved seven case-patients lived in a high-rise building in September 2021. We used a simplified tracer-gas experiment and virus sequencing to establish the link between case-patients. Vertical transmission among vertically aligned apartments on different floors in a building was the most likely route of transmission.

Time trends and modifiable factors of COVID-19 contact tracing coverage, Geneva, Switzerland, June 2020 to February 2022

BackgroundContact tracing was one of the central non-pharmaceutical interventions implemented worldwide to control the spread of SARS-CoV-2, but its effectiveness depends on its ability to detect contacts.AimEvaluate the proportion of secondary infections captured by the contact tracing system in Geneva.MethodsWe analysed 166,892 concomitant infections occurring at the same given address from June 2020 until February 2022 using an extensive operational database of SARS-CoV-2 tests in Geneva. We used permutation to compare the total number of secondary infections occurring at the same address with that reported through manual contact tracing.ResultsContact tracing captured on average 41% of secondary infections, varying from 23% during epidemic peaks to 60% during low epidemic activity. People living in wealthy neighbourhoods were less likely to report contacts (odds ratio (OR): 1.6). People living in apartment buildings were also less likely to report contacts than those living in a house (OR: 1.1-3.1) depending on the SARS-CoV-2 variant, the building size and the presence of shops. This under-reporting of contacts in apartment buildings decreased during periods of mandatory wearing of face masks and restrictions on private gatherings.ConclusionContact tracing alone did not detect sufficient secondary infections to reduce the spread of SARS-CoV-2. Campaigns targeting specific populations, such as those in wealthy areas or apartment buildings, could enhance coverage. Additionally, measures like wearing face masks, improving ventilation and implementing restrictions on gatherings should also be considered to reduce infections resulting from interactions that may not be perceived as high risk.