New study questions the effectiveness of masks against SARS-CoV-2

All data and statistics are based on publicly available data at the time of publication. Some information may be out of date. Visit our coronavirus hub and follow our live updates page for the most recent information on the COVID-19 outbreak.

In an effort to find more ways of slowing the COVID-19 pandemic, researchers and public health officials around the world have been debating whether using face masks in public might help.

This is a long and fraught debate, and international specialists and decision makers have not reached a consensus.

Earlier this month, the Centers for Disease Control and Prevention (CDC) issued new guidelines on the use of face masks by the public.

The guidelines encourage people to wear homemade cloth masks while out and about, while still urging them to leave specialized surgical masks and N95 respirators to medical professionals, who have been facing a dangerous shortage.

At the same time, the World Health Organization (WHO), which have also updated their guidelines for the use of protective face masks, warn instead that “The wide use of masks by healthy people in the community setting is not supported by current evidence and carries uncertainties and critical risks.”

So what does the latest scientific evidence indicate?

More virus on outer mask surfaces

According to a study recently published in Nature and covered by Medical News Today, surgical masks may go some way toward preventing a person with a viral respiratory infection from spreading infectious particles.

However, while the study did look at coronaviruses, it did not account for SARS-CoV-2, as the initial research had taken place before the start of the current pandemic.

Now, new findings, published in the Annals of Internal Medicine, suggest that neither surgical nor cloth masks are at all effective in stopping the spread of SARS-CoV-2.

The research, conducted by investigators from the University of Ulsan College of Medicine, Chung-Ang University Hospital, and Sejong University — all in Seoul, South Korea — involved a group of four participants receiving medical care for COVID-19.

To find out whether — and which — masks could stop the viral particles from spreading, the researchers asked the participants to cough over petri dishes without a mask, while wearing a disposable surgical mask, and while wearing a reusable mask made of cotton cloth.

In each of these three circumstances, the participants had to cough five times. Each time, they did so over a different petri dish.

Finally, the team swabbed the outer and inner surfaces of each mask — cotton or surgical.

They expected to find droplets containing SARS-CoV-2 on the inner surfaces. The question was whether any viral particles had been able to pass through the masks to their outer surfaces.

After analyzing the swabs, the researchers found particles of SARS-CoV-2 on the outsides of both types of mask, suggesting that neither type can contain the virus.

“Neither surgical nor cotton masks effectively filtered SARS–CoV-2 during coughs by infected patients,” the researchers write in their study paper.

Prior evidence that surgical masks effectively filtered influenza virus informed recommendations that patients with confirmed or suspected COVID-19 should wear face masks to prevent transmission,” they explain.

The team goes on to note that, while it remains unclear just how large particles containing SARS-CoV-2 and carried by the breath are, estimates regarding the size of a similar coronavirus, SARS-CoV, suggest that “Surgical masks are unlikely to effectively filter” it.

The researchers, moreover, emphasize that:

“Of note, we found greater contamination on the outer than the inner mask surfaces. Although it is possible that virus particles may cross from the inner to the outer surface because of the physical pressure of swabbing, we swabbed the outer surface before the inner surface. The consistent finding of virus on the outer mask surface is unlikely to have been caused by experimental error or artifact.”

This study did not aim to verify whether surgical or cloth masks are able to shorten the trajectory of droplets emitted through coughing.

Nevertheless, based on their findings so far, the investigators conclude that surgical masks and reusable cloth masks are both “ineffective in preventing the dissemination of SARS-CoV-2.”