How Use of Face Masks Might Reduce the Severity of Covid-19 Disease
Universal facial masking is deemed as one of the pillars of Covid-19 pandemic control. A recent NEJM perspective wrote about how facial masking might help reduce the severity of the Covid-19 disease while we wait for the arrival of a safe vaccine. Well, what does that mean? How does even one assess the reduced magnitude of disease severity? Reduced level of disease severity, at the very least for Covid-19, means decreased numbers of critically ill patients who would perhaps experience breathing issues requiring ventilation in the ICUs, among other things. It also essentially means that a greater proportion of new infections are asymptomatic or not symptomatic. Now, a lot of these thinking are early data-driven hypotheses; nonetheless, they make a lot of sense. If these early data (summarized below) are true, then universal masking could generate sufficient immunity to slow the spread of the virus globally, placing us in a much better position once the vaccines arrive to ultimately help us get back to normalcy.
At the beginning of April, the Centers for Disease Control and Prevention (CDC) recommended everyone wearing cloth face coverings in areas with high rates of community transmission. The reason being, infectious viruses are shed from the noses and mouths of infected individuals even if they are asymptomatic or pre-symptomatic. Data has shown that the shedding rates of viruses from asymptomatic individuals are comparable to those who are symptomatic.1 Despite all the evidence, CDC’s recommendation has not been widely practiced across the United States.
Data related to other respiratory viruses published in the peer-reviewed journals indicate that facial masking can also protect one from getting infected, and thereby prevent sickness and subsequent spreading. This protection is achieved by blocking viral particles from entering through the nose and mouth.2 Based on a global epidemiological study in countries that adopted population-wide masking during the 2003 SARS pandemic, there seems to be a strong relationship between public masking and pandemic control. More recently, data from Boston, Massachusetts showed that SARS-CoV-2 infections decreased among health care workers after the implementation of universal masking in municipal hospitals back in March 2020.
Furthermore, recent data have led to the belief that facial masking may also reduce the degree of disease severity among people who do get infected.3 Typically in viral pathogenesis the severity of the disease is dependent upon the viral inoculum (size/concentration of exposed infectious particles) received. The body’s immune responses play a central role in the viral pathogenesis of SARS-CoV-2 or the coronavirus. High doses of viral inoculum can overwhelm and dysregulate our innate or first line of immune defenses, which increase the severity of the disease. In animals, higher doses of viral infection have led to more severe manifestations of Covid-19 in a Syrian hamster model of coronavirus infection.4 This is why down-regulating the immune system is one strategy that can improve outcomes in severe Covid-19 infection.
These data potentially tell us that viral inoculum is a big factor in causing the severity of Covid-19. If this is true, then it speaks volumes for wearing facial masks, which could lead to reduced viral inoculum to which an individual is exposed to. Many studies have shown that masks can filter out some virus-containing respiratory droplets, although depending on the mask types. Therefore, population-wide masking might lead to an increased proportion of asymptomatic infections. NEJM stated that the typical rate of asymptomatic infection with Covid-19 coronavirus is about 40% by the CDC in mid-July, while asymptomatic infection rates are reported to be greater than 80% in settings where universal facial masking is followed—providing initial evidence for this hypothesis. Countries that have adopted population-wide masking have fared better in terms of rates of severe COVID-related illnesses and death, perhaps suggesting a shift from symptomatic to asymptomatic infections. An interesting experiment in the Syrian hamster model with simulated surgical masking demonstrated the animals were less likely to get infected. In the case these animals did get infected, they either were asymptomatic or had milder symptoms compared to unmasked controls.
Masking leads to increased asymptomatic infection in an outbreak on a closed Argentinian cruise ship, where passengers were provided with surgical masks and staff with N95 masks. The rate of asymptomatic infection was 81%. In an earlier cruise ship outbreak without the use of masks, the rate was 20%. Similarly, two outbreaks in U.S. food-processing plants, where all workers were required to wear masks, the proportion of asymptomatic infections among about 500 people who got infected was 95%; only 5% in each outbreak experienced mild-to-moderate symptoms.3 Fatality rates in countries with mandatory or enforced population-wide masking have remained low, even with resurgences of cases after lockdowns were relaxed.
This fight against the Covid-19 pandemic will involve crippling both the transmission rates and the severity of the disease. Increasing evidence is suggesting that population-wide masking might benefit both of these components. It makes a lot of sense to use measures that can reduce both components to spare the devastating effects of the disease, including long-term risks and death. We can’t be comparing the seasonal flu virus to this coronavirus. SARS-CoV-2 is highly transmissible, and it cannot be contained by symptom-based surveillance alone.1 It is already proving difficult to eradicate the Covid-19 virus even with strict public health measures. At this point, we are looking beyond just infection prevention strategies with vaccines. Most vaccine studies are looking into secondary outcomes of reducing disease severity; even increasing the number of cases that are mild or asymptomatic would be considered a public health victory. Based on limited but promising data, universal masking seems to reduce the rate of new infections. As we wait for a Covid-19 vaccine, it is worth it to implement measures that can make SARS-CoV-2 infections less deadly, boost population-wide immunity, reduce the severity of illnesses, and minimize the number of deaths. To know for sure, we will need further investigation into comparing asymptomatic infection rates in areas with and without universal masking.
Stay up-to-date with the latest advancements in the development of COVID-19 Vaccines (this post is frequently updated in our blog), and the Covid-19 Vaccine Distribution Plan. You may also find our post on an expert perspective on Will there be an End to Covid-19 helpful.
Sources:
Gandhi M, Yokoe DS, Havlir DV. Asymptomatic transmission, the Achilles’ heel of current strategies to control Covid-19. N Engl J Med 2020;382:2158-2160.
van der Sande M, Teunis P, Sabel R. Professional, and home-made face masks reduce exposure to respiratory infections among the general population. PLoS One 2008;3(7):e2618-e2618.
Gandhi M, Beyrer C, Goosby E. Masks do more than protect others during COVID-19: reducing the inoculum of SARS-CoV-2 to protect the wearer. J Gen Intern Med 2020 July 31 (Epub ahead of print).
Imai M, Iwatsuki-Horimoto K, Hatta M, et al. Syrian hamsters as a small animal model for SARS-CoV-2 infection and countermeasure development. Proc Natl Acad Sci U S A 2020;117:16587-16595.
You may also like the following posts:
Coronavirus (COVID-19) Vaccines Latest Updates
Can a 90% Effective Pfizer/BioNTech COVID-19 Vaccine Stop the Coronavirus Pandemic?
Understanding the Benefits and Limitations of Remdesivir: First FDA-Approved Drug for Covid-19
Will there be an End to Covid-19, Coronavirus? An Expert Perspective
How Use of Face Masks Might Reduce the Severity of Covid-19 Disease
Post-COVID Coronavirus Effects in Children and Babies Appear to Be Far Worse Than We Thought
Long-term Effects and Risks of COVID-19
COVID-19 Vaccine Distribution Plan
For the Physicians: Tips for Patients’ Concerns About Office Visits During a Pandemic
There Is No Link Between Vaccines and Autism. Myth Debunked
Getting Tested for Coronavirus Before Traveling
4 Questions You Must Ask When Sending Your Kids Back to School During the Pandemic
Featured Guest: Dr. Nahreen Ahmed shares her perspective on A "Typical" Day in the Covid ICU
