Masks Help to Prevent Infections with Respiratory Viruses

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Refusing to wear a mask when you have a respiratory infection and are near other people shows total disregard for their health. We have just gone through the major portion of a COVID-19 epidemic and can expect other epidemics from this and other viruses in the future. Many studies show that a proper mask will block some of the viruses, and droplets spread when an infected person coughs, sneezes, breathes or talks (Phys Fluids, Dec 1, 2020;32(12):127112). Before COVID-19, several studies showed that masking helped to reduce transmission of related betacoronaviruses, SARS and MERS (Lancet, 2020;395(10242):1973-1987).

Several studies have shown increased protection with greater consistency of masking (MMWR Morb Mortal Wkly Rep, 2022;71(6):212-216). The best and most comprehensive review of the world’s scientific literature demonstrates that wearing face masks reduces the spread of SARS-CoV-2 (JAMA Netw Open, Oct 31, 2023;6(10):e2339443). The authors quote many of these studies; see the list of references below.

Types of Face Masks
Cloth masks: usually contain several layers of fabric with ear loops or head ties. They should be worn in public by anyone who has symptoms of a respiratory infection. However, they offer little protection from disease for healthy people.

Surgical masks: usually constructed better than most cloth face masks, but offer minimal protection from infection for people who do not have a respiratory infection. They are usually light blue and are made from paper and plastics.

Respirators: help to protect healthcare workers from inhaling virus and droplets in the air. They must be fitted for each wearer so they fit tightly on the face to block both inspired and expired air. The types include:
• N95 masks, manufactured in the U.S., can filter out at least 95 percent of very small particles such as bacteria and viruses.
• FFP2 face masks, made in Europe, meet World Health Organization (WHO) guidelines for protection against COVID-19 and can filter at least 94 percent of particles for up to eight hours.
• FFP3 masks filter at least 99 percent of particles but usually need to have a valve because of the thick filtration material.

Why Some Studies Failed to Show that Masks Prevent Infection
• It would be immoral to design a study during a major pandemic in which people in a control group did not wear masks, which would increase their exposure to a potentially fatal disease.
• In some failed studies, only four percent of participants told to wear masks reported that they wore masks as recommended (Ann Intern Med, 2023;176(6):827-835. doi:10.7326).
• In large population studies during a major epidemic, it is impossible to check how often people wear masks. Some studies failed to check whether masks were worn all the time or only just before a person in that household developed respiratory symptoms.

Objections to Wearing Masks
• Masks can be uncomfortable and fog up glasses
• Masks can cause difficulty breathing in people with respiratory problems
• Masks can make it difficult to breathe during intense exercise
• Masks may not be available and can be difficult to fit, particularly for children

Other means of preventing infection are also important:
• Vaccinations
• Isolation of infected people
• Frequent hand washing
• Avoiding crowded places, particularly indoors, and particularly for high-risk individuals

My Recommendations
Most people have relaxed the precautions they took during the height of COVID-19, but people who are at risk for respiratory infections should continue to use masks when appropriate. Anyone who has a respiratory infection owes other people the protection of isolation, or at minimum, wearing a mask, since you spread germs with every breath. If you must be exposed to people with respiratory infections, they and you should both wear masks. Respiratory viruses continue to accumulate over time in closed spaces such as in stores, meeting places, planes, buses, trains, cars and so forth.

References
• Widespread community masking in 600 villages in Bangladesh covering more than 340,000 residents was associated with a statistically significant reduction in symptomatic SARS-CoV-2 infections (Science, 2022;375(6577):eabi9069).
• Cloth masks, surgical masks, and N95 respirators reduced the spread of potentially infectious respiratory droplets and aerosols (mSphere, 2020;5(5):e00637-20; MMWR Morb Mortal Wkly Rep, 2021;70(7):254-257; Nat Med, 2020;26(5):676-680).
• Masks helped to reduce transmission of SARS-CoV-2 on airplanes (J Travel Med, 2020;27(8):ta178), in schools (MMWR Morb Mortal Wkly Rep, 2021;70(39):1377-1378; MMWR Morb Mortal Wkly Rep, 2021;70(39):1372-1373), among households (BMJ Glob Health, 2020;5(5):e002794) and among community contacts of individuals with COVID-19 (Clin Infect Dis, 2022;75(1):e276-e288).
• Funding for studies to test whether masks prevent disease during major epidemics is extremely limited (N Engl J Med, 2013;368(13):1251-1255).
• Available evidence strongly suggests that masking in the community can reduce the spread of SARS-CoV-2 and that masking with the highest-quality masks that can be made widely available should play an important role in controlling whatever pandemic caused by a respiratory pathogen awaits us (J Clin Diagn Res, 2016 Jul; 10(7): OC06-OC08).