The spread of macroscopic droplets from a simulated cough with and without the use of masks or barriers

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.

Effects of upper respiratory tract anatomy and head movement on the buoyant flow and particle dispersion generated in a violent expiratory event

In the wake of the COVID-19 pandemic, interest in understanding the turbulent dispersion of airborne pathogen-laden particles has significantly increased. The ability of infectious particles to stay afloat and disperse in indoor environments depends on their size, the environmental conditions and the hydrodynamics of the flow generated by the exhalation. In this work we analyze the impact of three different aspects, namely, the buoyancy force, the upper airways geometry and the head rotation during the exhalation on the short-term dispersion. Large-Eddy Simulations have been used to assess the impact of each separate effect on the thermal puff and particle cloud evolution over the first 2 s after the onset of the exhalation. Results obtained during this short-term period suggest that due to the rapid mixing of the turbulent puff, buoyancy forces play a moderate role on the ability of the particles to disperse. Because of the enhanced mixing, buoyancy reduces the range and increases the vertical size of the small particle clouds. In comparison to the fixed frame case, head rotation has been found to notably affect the size and shape of the cloud by enhancing the vertical transport as the exhalation axial direction sweeps vertically during the exhalation. The impact of the upper airway geometry, in comparison to an idealized mouth consisting in a pipe of circular section, has been found to be the largest when it is considered along with the head rotation.