Respiratory Source Control

A small randomized clinical study was conducted in FranceFrance to investigate the effectiveness of surgical masks for reducing spread of influenza A in the household. The index case of each household who tested positive for influenza A was randomised to wear or not wear a mask. The study tested the association between the intervention (mask wearing) and the proportion of household contacts that developed an influenza-like illness. The study did not find a trend suggesting the effectiveness of face masks but the authors stated that there was a lack of statistical power.

Researchers at the Department of Ocean and Mechanical Engineering at Florida Atlantic UniversityFlorida Atlantic University examined the blocking of emulated coughs and sneezes by different mask materials and designs using qualitative visualizations of vapors creating by a fog machine. The research showed that loosely folded face masks and bandana-style covering provided minimal blockage and well-fitted homemade mask with multiple layers of quilting fabric and off-the-shelf cone style masks were most effective at reducing droplet dispersal.

A study on household interventions to prevent upper respiratory tract infections was conducted by researchers at Columbia UniversityColumbia University, New York, found that mask wearing was associated with reduced secondary transmission.

Stony Brook University Medical Center, New YorkNew York

Duke University

Duke University

Mathematical modelling research from Hong Kong Baptist UniversityHong Kong Baptist University suggested that if face coverings that were 60% effective at blocking viral transmission were worn by 60% of the population the transmission rate R0 would be reduced to below 1.0.

In a hair salon in Springfield, MissouriSpringfield, Missouri, it was reported that 139 clients were exposed to two hair stylists with confirmed COVID-19 while both the stylist and client wore masks and there were no symptomatic secondary cases reported. 67 of the exposed clients were tested for SARS-CoV-2 and tested negative.

Researchers at the University of Hong Kong concluded that community-wide mask wearing may contribute to the control of COVID-19. Over the period from December 31, 2019 to April 8, 2020, the compliance of face mask usage was 96.6% in HKSAR and incidence of COVID-19 in HKSAR was significantly lower than that in other countries such as SpainSpain and the U.S. where compliance for face masks was low.

In a hair salon in Springfield, Missouri, it was reported that 139 clients were exposed to two hair stylists with confirmed COVID-19 while both the stylist and client wore masks and there were no symptomatic secondary cases reported. 67 of the exposed clients were tested for SARS-CoV-2 and tested negative.

The above illustration shows how a mask worn as source control will act as a barrier to reduce the amount of virus-laden droplets released outward from an infected individual.

GRAPHIC: V. ALTOUNIAN/SCIENCE, Source: K. A. Prather et al., Science 10.1126/science.abc6197 (2020)

The above illustration shows how a mask worn as source control will reduce the amount of virus-laden droplets released from an infected individual.

The above is a photo from a high-speed visualization that illustrates airflow when coughing. It shows that the cough stays closer to the face when a person wears a face covering. The illustration does not show the movement of virus particles but is a technique that shows the differences in airflow between not wearing a mask and wearing a mask. Mathew E. Staymates, a NIST researcher used his technique to visualize airflow for a variety of face coverings worn by people during coughing. The group observed that wearing many types of face covering reduced airflow velocity when people were talking. See section "Reducing distance air travels from mouth".

National Institute of Standards and Technology (NIST)/ Matthew E. Staymates

NIST researchers produced a video comprised of high-speed visualizations that illustrate airflow when breathing and coughing using homemade face coverings. The research team found that most face covering stopped much of the cough from landing on someone else and that a good seal around the nose, chin and cheeks prevents leaking. They were able to visualize that a surprising amount of air comes out of the nose during a cough, indicating that covering the nose if important.