Cloth face masks can reduce COVID-19 spread, new study shows

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In a new review study, researchers found that cloth face masks provide clinically useful levels of filtration, which has the potential to reduce the spread of viruses such as SARS-CoV-2.

The findings support the wearing of cloth masks to reduce the spread of the new coronavirus.

The research was conducted by a team at Karolinska Institutet in Sweden and McMaster University in Canada.

The research group identified 25 published articles that studied the filtration properties of cloth or cloth face masks of various designs and materials.

The testing behind the articles had been conducted in various ways and using different methods, making them difficult to compare.

Few of the studies followed existing medical standards for certifying personal protective equipment intended for use in healthcare.

Despite this, according to the researchers, the results convincingly demonstrate that certain cloth face masks reduce the spread of particles to the wearer’s surroundings and reduce the particles inhaled.

The team says it may seem counterintuitive that woven cloth, with space between threads that are visible to the naked eye, can block fine particles in the aerosol size range, but the data show unequivocally that this is the case.

Even single layers block some particles and multiple layers perform better.

They believe the use of face masks should be a key component of reducing the spread of COVID-19, which is in line with current recommendations from the WHO and the CDC in the United States.

The same research group published a commentary in the Annals of Internal Medicine in late May, recommending the use of cloth face masks for the public.

At the same time, the researchers emphasize the importance of good hand hygiene, social distancing, and disinfecting public areas.

In the study, the materials demonstrated to offer the best protection were muslin (a type of unfinished cotton), cotton and flannel, preferably in three to four layers, and with a thread count of at least 100 threads per inch (TPI).

For example, a historic surgical face mask made of 4-layers of muslin reduced contamination of the air to the same extent as disposable medical face masks, even for fine particles in the aerosol size range.

The team says scientists have no direct proof that face masks reduce the transmission of SARS-CoV-2, as this would require a randomized clinical trial that would be unethical to conduct.

However, the current review shows clearly that face masks can reduce the spread of viruses and protect the wearer—some of them highly effective.

This evidence should be more than sufficient to recommend their use, particularly given the difficulty in controlling the ongoing pandemic.

One author of the study is Juan Jesus Carrero, a professor of epidemiology at the Department of Medical Epidemiology and Biostatistics.

The study is published in the journal Mayo Clinic Proceedings.

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