Face masks have been a lightning rod for national debate and public conflict. Airlines require flight crews and passengers to wear masks on airplanes. Retail outlets require customers to wear masks when shopping. University campuses require students, faculty, and staff to wear masks as a condition for reopening in the fall. The list of venues that require masks for entrance or service continues to grow.
Public health argues that masks slow the spread of the virus. Others label masks as a left-wing hoax, a violation of their constitutional rights and individual freedoms. Wearing a mask is like wearing seat belts. Most of the time, it makes no difference, but occasionally, it saves lives, if worn correctly as with seat belts, the biggest issue is not whether you choose to wear a mask, but how you wear your mask.
A trip to any grocery store will provide a glimpse into the breadth of ways that people are wearing masks. Some have their mask around their neck or chin, much like an ascot, while others only cover their mouth. The number of people who have their mask covering both their mouth and nose is in the minority. Given that COVID-19 is a respiratory illness, transmitted by droplets from the nose or mouth of an infected person, any mask that does not cover both the nose and mouth is not serving its intended purpose.
There are numerous reasons why people remove their masks in public. The three most common reasons are to eat, to drink, or to smoke. People also sometimes drop their mask to speak to someone, or because their eyeglasses become foggy.
Then there is the type of masks that people wear. N95 masks, the gold standard for face masks, are in short supply, with those available allotted to healthcare workers and first responders. For most people, these masks are not accessible. That leaves people with surgical or cloth masks, many of which are handmade, following CDC guidelines. A recent article in the Annals of Internal Medicine noted that there is low certainty evidence to establish that masks prevent virus transmission in the community setting. A recent article in the Lancet further corroborates this opinion. I would argue that there is no strong evidence because there is no ethical way to design a clinical trial to make such an inference. A National Academies report notes that surgical and cloth masks may help suppress the emission of viral droplets from an infected person with influenza. At the same time, there is no evidence that these masks protect an uninfected person from becoming infected. Therefore, people who wear these masks are not doing so to protect themselves, but rather protect others if they happen to be asymptomatic or presymptomatic, yet contagious.
The best one can conclude from all this research and discussion that people wearing masks demonstrate an altruistic concern for others. They likely receive no personal protection yet provide great benefit to others. This was most apparent when two hairstylists in Missouri who were infected exposed 140 clients to the virus, yet none became infected.
Masks slow the spread of COVID-19. To be effective, they must be worn correctly, covering both the mouth and nose and consistently whenever close to other people. If a person is either unwilling or unable to meet these criteria, then the best strategy is to stop wearing a mask. Others can take the necessary actions to stay sufficiently far away not to get exposed. Just like seat belts, masks save lives, but only if worn correctly.
Sheldon H. Jacobson, Ph.D., is a founder professor of Engineering in the Department of Computer Science and the Carle Illinois College of Medicine at the University of Illinois at Urbana-Champaign. He applies his expertise in data-driven risk assessment to evaluate and inform public policy and public health.