Masks still work to reduce the transmission of respiratory disease

As we dive deep into a new wave of COVID-19 infections this winter, the value of masking is back in public discourse. This is an especially important topic after much of the preventive efforts seem to have been suspended after more than two years of the pandemic.  A viral tweet shared by thousands makes the following claim: “If face masks worked, China wouldn’t be seeing such numbers…”. It then goes on to claim that “there’s no evidence that mask mandates helped reduce infections anywhere. The largest of the school studies showed they made no difference in those settings either.”

Back in March, Newswise refuted the claim that masking does “nothing.” As we mentioned before, several studies have shown that widespread mask-wearing is associated with reductions in disease transmission of COVID-19 (See here, here, and here). Therefore, the claim that masks don’t work is entirely false. 

Chris Cappa, Chair of the Department of Civil and Environmental Engineering, University of California, Davis, debunks the claim that masks don’t work and why we’re seeing high rates of COVID in China…

We know that masks help to reduce transmission of respiratory disease by blocking the particles that carry respiratory viruses. The evidence for this is unequivocal. Yet, we know that the overall effectiveness of mask wearing depends importantly on the type of face mask worn and how well a mask is worn. High-quality, well-fitting respirators worn properly provide substantially more protection than other mask types, such as surgical masks or cloth masks. Regardless, if masks are even 50% effective, which is about the effectiveness of many surgical masks, they can have major public health benefits. But, a 50% intervention alone cannot completely eliminate risk or reduce transmission to zero.

The currently high rates of COVID in China are in many ways expected as people start to interact across households to a much greater extent than they have in the recent past. Mask wearing by the public can and does absolutely help reduce the rates of transmission. But masks alone cannot eliminate transmission risk entirely.

Greg Schrank, MD, MPH, who serves as an Associate Hospital Epidemiologist at the University of Maryland Medical Center and Assistant Professor of Medicine at the UM School of Medicine, tells us how masking works to slow the spread of the coronavirus and other air-borne diseases…

One of the primary ways that respiratory viruses are transmitted between people is by traveling through the air on small particles. These particles appear to be more stable in the air when the weather is cooler and drier, like in wintertime. Coupled with the indoor gatherings of the holidays, it makes winter a much more active time for respiratory viruses. Well-fitting, multi-layered masks work to protect the wearer by filtering out the small particles containing the viruses. If someone is infected with a virus, the masks work by containing these particles and preventing them from spreading out into the surrounding environment. This is especially true in crowded or confined spaces with poor ventilation, where infectious particles accumulate in the air, leading to transmission. Though cloth masks may provide some benefit, the most effective masks are those that are multi layered, cover your nose and mouth completely, and are well-fitting, preventing gaps around the nose or sides of the face. These masks are better at filtering the aerosols (fine particles) that contain the virus and better prevent transmission as compared to cloth masks. A well-fitting procedure/surgical mask, KN95, or N95 are all examples of these higher quality masks that fit and filter better than a cloth mask.