Do masks prevent the spread of coronavirus?

Medically reviewed by Neka Miller, PhD on September 24, 2020. To give you technically accurate, evidence-based information, content published on the Everlywell blog is reviewed by credentialed professionals with expertise in medical and bioscience fields.

Masks and other face coverings remain some of the most important tools in reducing the spread of the coronavirus in the current pandemic. However, many people either don’t believe in the effectiveness of masks or do not wear them properly. So do masks actually prevent coronavirus? The answer is "yes." Read on to find out why—plus learn key information on types of masks and how to properly wear one.

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How face masks work

Face masks have commonly been used in China, Japan, Korea, and other East Asian countries even prior to the novel coronavirus pandemic, and they are more than just fashion accessories. When you sneeze, cough, talk, or even just breathe, you emit respiratory droplets. These droplets are mostly composed of spit, mucus, and salt, but if you are infected, viruses, bacteria, or other potentially dangerous microbes can travel on the droplets. Aerosols, which are the smallest of these droplets, can potentially hover in the air for hours, exposing anyone who walks into that airspace, while the larger droplets can travel a few feet before dropping to the floor.

Masks work in a few different ways to prevent the spread of the virus. First, if you are infected, a mask can prevent you from infecting others by creating a physical barrier for any droplets you create, reducing the number of droplets that actually enter the air and minimizing the distance that they can travel. For those who are not infected, masks inhibit the inhalation of viral droplets that might be hanging in the air.

While face masks are mostly designed as a barrier against virus transmission, they also act as a physical hindrance for another method of transmission: touching your face. Although respiratory droplets are considered the main mode of transmission for the virus, there is still a risk of getting the virus by making contact with an infected person or surface, and then touching your nose or mouth. A mask can prevent the habit of face touching.

Types of face masks

Surgical masks

Surgical masks are loose, disposable masks designed for single-use after interacting with a patient. They create a light but effective barrier between the face and respiratory droplets, and other contaminants in the air.

Surgical masks come in varying degrees of thickness, and when worn properly, surgical masks can effectively block spray, splashes, and large droplets. However, by design, surgical masks do not strictly act as “filters,” and they do not form a tight seal around the mouth and nose.

Cloth masks

The most common and accessible type of mask for the average person, cloth masks, are face coverings that are usually made from cotton. Simple in design and mechanism, cloth masks help to trap any droplets that you may release when you talk, cough, or sneeze. A cloth face mask may not be as effective as medical-grade masks or the N95 masks described below, but they can help to contain droplets. Some studies even show that covering a mouth with just a washcloth can block nearly all droplets from a person’s mouth.

The biggest positive to cloth masks is their ease of use. You don’t need any specialized material. A homemade mask such as a simple handkerchief over the mouth and nose can make a significant difference in the fight against COVID-19. Cloth masks are also reusable.

N95 respirator masks

Considered the best of the best, the N95 respirator mask is a respiratory protective device that effectively filters out nearly all airborne particles. The “95” in N95 refers to the fact that these masks have been tested to filter out 95 percent of microbes and any particles measuring 0.3 microns in diameter.

Similar to surgical masks, N95 filters are not designed to be reused. Once they get wet, damaged, or dirty, they must be thrown away. N95 masks are also much more fitted than other options. They create a tight seal around the mouth and nose, which helps to prevent viral particles from leaking in or out, but it can also be a bit uncomfortable for long-term use.

Note that the CDC does not recommend N95 respirators for use by the general public. This is because supplies of N95 masks are limited and should be “reserved for health care workers and other medical first responders.”

What face mask is best?

Determining what type of face mask to use for coronavirus has been a recent topic of discussion. In terms of mechanisms of function, the N95 is the most effective at inhibiting the transmission of viral droplets. This is mainly due to the filtration system, which is made up of a dense tangle of zig-zagging filaments. This means there is no direct line through the mask. Any viral particles that do make it into the mask have to travel through a maze of tunnels and pathways while fighting against natural air currents. Larger particles get stuck in the filaments simply because they are unable to make sharp turns or pivots. Smaller particles have to contend with oxygen molecules, which bounce around and collide with the particles. A particle that is 0.3 microns in diameter could potentially make it into the mask, but getting completely through it is highly unlikely.

With that said, cloth masks are still effective, too. A study used publicly available data to determine the growth rate of COVID-19 in 15 states and the District of Columbia from March to late May 2020. The results showed that areas that had mask mandates were associated with a statistically significant slowdown in the daily growth rate of COVID-19 cases, with some estimates suggesting mask mandates prevented upwards of 450,000 total cases.

The average SARS-causing coronavirus is about 0.08 to 0.14 microns in diameter, which is generally smaller than a cloth mask can filter. However, viruses don’t come out of your body alone. They travel with droplets that are composed of spit and mucus. Respiratory droplets can be as large as 0.6 to 1,000 microns, which can be too large to get through the tiny holes of cloth masks.

While an N95 mask might be the most effective, a cloth face covering is better than no face covering at all as it does provide a physical barrier (and N95 mask usage is not recommended for the general public). The key is for everyone to wear a mask in public when possible—the greater the number of people wearing a mask, the less potential to spread the virus.

How to use a mask properly

Of course, just owning a mask is not enough. Wearing one properly can make all the difference. Here are some tips to boost the effectiveness of mask-wearing:

  • Wash your hands before and after using your mask.
  • Handle the mask only by the elastic bands or ties.
  • Make sure that both your mouth and nose are covered for complete protection.
  • Reusable masks should be washed after each use. Disposable masks should be discarded when they appear wet, soiled, or damaged.
  • Do not take your mask off in public.

Most importantly, a mask does not completely erase the risk of transmission on its own. It is meant to be used in conjunction with safe social distancing practices, handwashing, and testing. The importance of social distancing has become increasingly more clear: if you are in a dense, crowded, indoor space, a mask will only provide so much help.

The messaging around masks in the early stages of the pandemic was confusing for some people, but it is now decisively known that you should wear a mask whenever you are in public to prevent the spread of the virus. Whether you’re social distancing in the workplace or in the grocery store, a mask is key for coronavirus prevention. Along with wearing a face mask, consider getting tested—which can help you determine if you have a coronavirus infection if you’ve been experiencing symptoms.

Experiencing COVID-19 symptoms and looking for relief? Get COVID-19 treatment online via Everlywell's Virtual Care offering.

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