What to do so that masks protect more against COVID-19 according to science

Face coverings or masks are placed on the face and ears to reduce the risk of catching the coronavirus or to prevent it from spreading to others. In addition to vaccination, distancing, and permanent cross ventilation, masks are key to reducing the transmission of the virus in communities. In the United States, scientists at the Centers for Disease Control and Prevention's Institute for Occupational Safety and Health conducted a study to provide guidance for increasing the effectiveness of masks in reducing the spread of respiratory infectious pathogens, including coronavirus.

The results were published by the American Journal of Infection Control (AJIC), the journal of the Association of Professionals in Infection Control and Epidemiology (APIC). Scientists identified specific combinations of respirators and fit modifications. They can be applied by healthcare workers, patients, and the general public to improve the fit and performance of respirators.

Masks are used to reduce the spread of infectious viruses such as SARS-CoV-2, which are transmitted through airborne aerosols and droplets produced during activities such as speaking, breathing, and coughing. Infected people can emit them even when they have no symptoms.

The US Centers for Disease Control and Prevention (CDC) recommends a multi-layer mask that covers the nose and mouth and forms a tight seal against the face. “The performance of masks as infection control devices depends both on the ability of the mask material to filter aerosols and how well the mask fits the wearer,” said Françoise Blachere, a research biologist at the National Institute for Occupational Safety and Health (NIOSH) and lead author of the article.

Blachere and his colleagues used both human volunteers and simulator mannequins to test the performance of multiple mask types, combinations, and modifications. Researchers conducted a series of experiments simulating people's coughs and exhalations, and then measured the effectiveness of the masks in blocking respiratory aerosols.

The results show that overlapping a three-layer cloth mask over a medical mask (double mask) or attaching a medical mask with an elastic band provided the best protection against respiratory aerosols. mark> Unmodified medical masks blocked cough aerosols 56% and exhalation aerosols 42%.

In contrast, placing a cloth mask over a medical mask blocked 85% of cough aerosols and 91% of exhalation aerosols. If a clamp is added over a medical mask, 95% of cough aerosols and 99% of exhalation aerosols are blocked.

The use of ear loops or an ear strap, or tying and tucking the mask in, also increased performance compared to unmodified medical masks. Two other fit modifications of the mask, crossing the ear loops, or placing a support under the mask did not increase performance.

“Since the beginning of the COVID-19 pandemic, there has been considerable confusion about the most effective use of masks, especially among the general public, to reduce the spread of infection,” said Ann Marie Pettis, president from the Association of Infection Control and Epidemiology Professionals. “The findings of the new study are important and timely because they identify specific and practical combinations of face masks and modifications that can improve fit and therefore reduce monthly the expulsion of infectious aerosols into the environment”

Since the beginning of the advance by the coronavirus, the population of different Asian countries included masks as part of prevention. In that region of the world they were more used to it. In Japan, masks were widely used in 1918 during the flu virus pandemic. In 1923, they were used again by the impact of the Great earthquake in the Kantō region.

Much later, in November 2002, another coronavirus emerged in China, now called SARS-CoV-1. Within a few months it spread throughout the world. At that time, there were Asian countries such as Hong Kong that encouraged the use of masks in public places, and it came to be perceived as a civic responsibility to care for others.

In 2012, the Middle East respiratory syndrome coronavirus (MERS-CoV) epidemic in Saudi Arabia once again brought face masks to the fore. That epidemic spread to 21 countries, including countries like Qatar, Jordan, and South Korea. In the latter country, 17,000 suspected cases of MERS-CoV and 38 deaths were registered, and the population used the masks until 2015 when the spread of the virus was already controlled. That recent history made it easy for people in Asia to increase their use of masks last January when the novel coronavirus that causes COVID-19 spread. The governments of Singapore, South Korea and Japan provided masks to the population.

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