The Simple Science Behind Why Masks Work

• The CDC continues to advise wearing face masks to prevent the spread of COVID-19.
• Masks work by creating a physical barrier to the spread of virus-containing respiratory droplets.
• Growing evidence supports their effectiveness.
• While many Americans have objected to wearing masks, experts say their concerns are unfounded.

The Centers for Disease Control and Prevention (CDC) continues to strongly advise the wearing of face masks to prevent the transmission of SARS-CoV-2, the virus that causes COVID-19.

On July 14, 2020 the CDC Director Dr. Robert Redfield said in a press release: “Cloth face coverings are one of the most powerful weapons we have to slow and stop the spread of the virus — particularly when used universally within a community setting.”

While these recommendations have been met with some skepticism among the public, scientific evidence continues to show that masks do work.

As to the reasons why, the experts say the science is quite simple.

Why face masks work

Transmission of the coronavirus is thought to occur through respiratory droplets that are released when people speak, sneeze, or talk, according to Dr. MeiLan Han, a professor of medicine in the division of pulmonary and critical care at the University of Michigan.

If these droplets land in the mouth or nose of people nearby, or are inhaled into the lungs, a person can contract the virus.

Masks create a physical barrier that catches these droplets and prevents them from spreading as far into the surrounding air as they normally would.

Han said the masks become even more important because a significant proportion of people who get COVID-19 either don’t exhibit symptoms or there’s a delay before symptoms show up.

Studies show, however, that these people can still transmit the virus to people around them.

The data suggest that the use of face coverings can help limit the spread of the disease by these asymptomatic and presymptomatic individuals, said Han.

Growing evidence supports mask effectiveness

In the July 14, 2020 issue of the Journal of the American Medical Association (JAMA), the authors of an editorial piece said that “the time is now” for universal mask wearing.

In support of their opinion, they pointed to two case studies that were published that same day.

The first study showed that a universal mask wearing policy in a Boston hospital system reduced the transmission of SARS-CoV-2.

Prior to the institution of the mask policy, new cases among healthcare workers who had either direct or indirect patient contact were increasing exponentially.

After the policy was put into place, however, the proportion of symptomatic healthcare workers who tested positive for COVID-19 “steadily declined,” according to the report.

The editorial additionally spoke about a report in the CDC’s Morbidity and Mortality Weekly Report (MMWR) which showed that wearing a mask appeared to prevent two Missouri hairstylists from spreading the disease to their customers.

Both stylists had continued to see customers for several days after developing symptoms, but wore face masks as per local government ordinance. Ninety-eight percent of their customers wore masks as well.

Of the 139 customers that the stylists saw before being diagnosed, none developed COVID-19 symptoms during the follow-up period. None of their secondary contacts developed symptoms either.

In addition, of the 67 clients who agreed to be tested, none were positive for the virus.

Answering the skeptics

Despite the scientific evidence supporting the wearing of masks, many Americans have voiced objections to their use.

We asked Dr. Vinisha Amin, hospital medicine physician at University of Maryland Upper Chesapeake Health to counter some of the more frequently raised concerns and misinformed myths that are currently being spread.

1. Masks don’t work

“Let’s disintegrate that myth!” said Amin. “Masks are helpful and effective in protecting you and your loved ones from the virus.”

“There is a plethora of scientific data and research to help solidify this recommendation,” she added.

“In the scientific world, evidence-based medicine takes precedence, and we must put trust in our physicians and scientific community when they make such recommendations given that they are for your own and your loved ones’ medical/health safety,” Amin said.

2. They’re so uncomfortable to wear

“That means you have only tried one mask and gave up quickly on finding one that works well,” said Amin.

“Yes, they may create humidity, but in that situation, wear a cotton material mask which is a more breathable material than polyester,” she advised.

“Yes, they might hurt your ears. In that situation find a mask where the elastic band that wraps around the ear is cloth covered or a softer elastic band which won’t irritate your skin,” she said.

“Yes, they fog up glasses. I have the same issue,” she added. “In that situation, place your eyeglasses over the mask on the bridge of your nose to help hold the mask in place and also help mitigate the fog under your glasses.”

3. I’m worried about carbon dioxide building up and making me sick

“There is absolutely no scientific reasoning that supports the claim that there is carbon dioxide buildup due to masks,” said Amin.

“Healthcare professionals such as our physicians and surgeons have been utilizing tighter and more impenetrable masks for decades, yet we are still able to breathe through them,” she said.

She continued, “Masks allow for oxygen to penetrate in just as readily as they allow for carbon dioxide to penetrate out.”

4. I’m not at high risk

Amin acknowledged that the most vulnerable people are those with comorbid conditions or those who are immunocompromised.

She noted, however, that “although you may be healthy and fit, you might not even be aware that you have acquired the virus and could be shedding high viral loads to your vulnerable loved ones at home.”

“We are all co-dependent on each other for our well-being and health as a community,” she explained.

The bottom line

There’s growing evidence that masks do work in preventing the spread of COVID-19.

Masks works in a very simple way by capturing the virus-containing droplets we emit when we speak, cough, or sneeze.

Although the principle behind masks is a simple one, they’re a very important part of containing the disease.

Experts say they work best when we all cooperate and wear them.

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