dcyphr | Face masks against COVID-19: an evidence review


Knowledge on masks and their ability to slow the spread of COVID-19 is constantly developing. Public officials need info on how masks can best be used by the public to fight the COVID-19 pandemic. COVID-19 is spread by droplets in infected people's lungs. These droplets are released outside the body through sneezing and coughing. Healthy people can contract COVID-19 if these infected droplets enter their bodies. Masks slow virus spread by limiting the movement of these droplets through the air. This article examines many other articles on mask-wearing to see if public mask-wearing is appropriate. The authors of this article urge public officials to encourage people to wear masks. Cloth masks are acceptable if medical masks are not available. 

1. Components to Evaluate for Public Mask Wearing

Before encouraging the public to wear masks, we should answer these questions:

- Can symptom-less people infect healthy people?

- Does mask-wearing prevent infected people from infecting healthy people?

- Are there masks that can be made without hurting the supply of medical masks?

- Will mask-wearing prevent the wearer from being infected?

- What are the overall effects of public mask-wearing?

2. Transmission Characteristics of COVID-19

COVID-19 is highly contagious, and is mainly spread through coughing, sneezing, and talking. A lot of people with COVID-19 show no symptoms. Almost all COVID-19 patients go through an initial stage where the virus replicates inside their bodies but they show no symptoms. This stage usually lasts 2 to 15 days. People are most infectious during the first few days after they are infected - when there are mild or no symptoms. Any public policies created to limit COVID-19 spread must consider people who can spread the virus while showing no symptoms.

3. Ingress: Filtering Capability of Masks

The designs and materials that make up face masks can affect how well they can block droplets from the wearer and how well they can reduce the wearer's risk of viral infection. One study showed that hospital workers with surgical masks were less likely to be infected by rhinovirus than workers with cloth masks. However, it is uncertain if the study's results can be applied to coronavirus. Another study shows that N95 respirators can filter virus particles better than surgical masks. However, people wearing N95 respirators and surgical masks were equally likely to contract influenza.

4. Egress: Masks for Source Control

When people cough, speak, and breathe, droplets are most of what comes out of their mouths. A small portion of these droplets come out in an evaporated form, or aerosols. Over time, emitted droplets evaporate to become aerosols. Masks catch droplets and prevent this from happening. Studies with virus-infected patients show that masks are effective in limiting both the amount of  virus particles in aerosols released from the mouth and the distance they travel. Studies also show that homemade masks are less effective, but they still work to some extent.

5. Evaluating Masks as an Intervention

This section details studies on interventions used during past virus outbreaks. These studies found that mask-wearing is an effective means of slowing public spread of viruses. The studies recommend combining mask-wearing with hand washing and physical distancing. Mask-wearing should begin at early stages of a pandemic. The section also details a report about a man with COVID-19 who wore a mask during a flight. Nobody near him contracted COVID-19 during the flight. This furthers the case for using masks as an intervention against COVID-19 spread.

6. Sociological Considerations

There are other issues with public mask-wearing aside from its effectiveness that officials should think over. People may think that masks are so effective, they can afford to ignore other measures meant to limit disease spread. However, studies suggest this is not a large concern. People may not wear masks because they don't want to be identified as sick. Employers may forbid their employees from wearing masks so they don't scare customers. Also, it can be hard to get all sick people to wear masks when some people don't know if they're sick or not. But if more people wear masks and if more places require people to wear masks, these issues may be lessened. People would be reminded of disease threat and feel a sense of unity from collectively wearing masks. Some of this can be seen in Hong Kong, where community activists banded together to increase mask-wearing.

7. Implementation Considerations

When enforcing public mask-wearing, there are several factors to consider. Different countries have different levels of access to resources. Some countries may have to consider whether public mask-wearing may limit the number of masks available to medical workers. In this case, citizens may be asks to wear medical mask alternatives. The public may not see a disease outbreak as a major threat. The amounts of mask-wearing people may change depending on whether mask-wearing is made mandatory. However, studies suggest that mandatory mask-wearing is effective at increasing public mask-wearing. Also, mask-wearing can defend against both current pandemics and other pandemics that can occur alongside them.

8. Estimating COVID-19 Impacts

This section discusses models that were made to predict COVID-19 spread with little, moderate, and high public mask-wearing. The effectiveness of mask-wearing is dictated by how well masks are made and how many people wear them. We measure infectivity of diseases with basic reproduction number, R0. COVID-19 has an R0 of 2.4, meaning that on average, an infected person spreads the virus to 2.4 other people. Good quality masks combined with high public mask-wearing can cut this number by almost half. The infection rate of a disease after interventions are made are measured with effective reproduction number, Re. Policy measures can shape public levels of mask-wearing and thus greatly impact Re. Models show that mask-wearing lowers infection rates at least somewhat, even when quality of masks and levels of mask-wearing are low. 

9. Discussions and Recommendations

The evidence examined throughout this article suggest that public-mask wearing is vital to slowing COVID-19 spread. Public officials should decide on interventions based on their cost and how well they can slow infection. Infections and economic impacts of COVID-19 decrease the more people wear masks in public. Clearer guidelines on mask-wearing can help slow and eventually stop the spread of COVID-19.

Materials and Methods

Researchers from different fields worked together to collect and examine papers for this review.