An article in the Morbidity & Mortality Weekly Report points out that universal masking is recommended to slow the spread of COVID-19 and that cloth masks and medical procedure masks significantly reduce exposure from infected wearers—source control—and reduce exposure of uninfected wearers—wearer exposure.
The new information from the CDC is the importance of fit in further reducing exposure. CDC researchers conducted experiments to assess two ways of improving the fit of medical procedure masks:
• Fitting a cloth mask over a medical-procedure mask, and
• Knotting the ear loops of a medical procedure mask and then tucking in and flattening the extra material close to the face.
“These experiments highlight the importance of good fit to maximize mask performance,” the CDC authors explain. “There are multiple simple ways to achieve better fit of masks to more effectively slow the spread of COVID-19.”
Background information in the articles notes that universal masking is one of the prevention strategies recommended by CDC to slow the spread of SARS-CoV-2, the virus that causes coronavirus disease 2019 (COVID-19). As of the beginning of February, the authors point out, 14 states and the District of Columbia had universal masking mandates and mask wearing had been mandated by executive order for federal property as well as on domestic and international transportation conveyances.
A problem, however, is that cloth masks and medical-procedure masks are more loose fitting than are respirators, such as N95 face-pieces. The CDC researchers suggest that the effectiveness of cloth and medical-procedure masks can be improved by ensuring that they are well fitted to the contours of the face to prevent leakage of air around mask edges.
During experiments conducted in January, the authors determined that 1) wearing a cloth mask over a medical procedure mask (double masking) and 2) knotting the ear loops of a medical procedure mask where they attach to the mask’s edges and then tucking in and flattening the extra material close to the face (knotted and tucked masks) improved fit and the receiver’s exposure to an aerosol of simulated respiratory droplet particles of the size considered most important for transmitting SARS-CoV-2.
Researchers emphasize that the receiver’s exposure was best reduced by more than 95% when the source and receiver were fitted with modified medical-procedure masks.
“These laboratory-based experiments highlight the importance of good fit to optimize mask performance,” the authors write. “Until vaccine-induced population immunity is achieved, universal masking is a highly effective means to slow the spread of SARS-CoV-2 when combined with other protective measures, such as physical distancing, avoiding crowds and poorly ventilated indoor spaces, and good hand hygiene. Innovative efforts to improve the fit of cloth and medical procedure masks to enhance their performance merit attention.”
The content contained in this article is for informational purposes only. The content is not intended to be a substitute for professional advice. Reliance on any information provided in this article is solely at your own risk.
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