Little to lose - time for everyone to wear face masks for COVID-19

By Dr. Liji Thomas, MDApr 12 2020

The CDC says it's time to encourage everyone to wear cloth face masks as a precaution against the spread of the COVID-19 disease pandemic. "We have little to lose, and potentially something to gain," say researchers in linked pieces in the prestigious journal, The BMJ.

Face masks for the public during the covid-19 crisis. Image Credit: Alexander Ishchenko / Shutterstock

Why are facemasks important?

On 4th April 2020, the U.S. Centers for Disease Control and Prevention (CDC) announced that the general public should wear cloth face masks.

COVID-19 is an illness that has no known vaccine or treatment, and it has spread across the globe at an unprecedented rate. Several studies have examined the efficacy of mask-wearing by the general public in widespread epidemics and pandemics. However, so far, none of them have provided conclusive evidence for or against these cheap devices.

One of these studies says, "With the exception of some evidence from SARS, we did not find any published data that directly support the use of masks by the public." A further study that was concluded on 6^th April 2020 stated that there was no conclusive evidence to support the widespread use of face masks against the spread of the coronavirus.

The World Health Organization (WHO) is ambiguous, stating that while masks do have a place among the general public during pandemics, they should generally be reserved for healthcare workers. However, matters have reached a point where many governments and agencies have gone ahead with recommending the routine use of masks in public places as a precautionary measure.

Studies have shown that the virus can remain viable in the air for several hours, and also that surgical masks may be able to block them to a certain extent. The maximum shedding of the coronavirus occurs in the early stages of the illness: victims may be contagious before they display symptoms. As many as 50% of new infections are caused by presymptomatic or asymptomatic cases. Sneezing or coughing only necessary to spread the virus: it can be dispersed by normal breathing. All these facts point indirectly to the advisability of generalized adoption of masks by the general public to protect against transmission.

As BMJ experts say, models derived from pandemics with similar respiratory spread suggest that "substantial numbers of cases may still be prevented even if masks are only 20% effective at reducing transmission."

Why oppose face masks?

Those who oppose this and similar recommendations base their opinions on four main grounds: firstly, they are not convinced that masks are effective. Secondly, they believe that masks should be reserved for healthcare workers. Thirdly, trials have shown that the public may not wear the masks correctly, requiring repeated readjustments (which defeat the very purpose, since the efficacy of masks depends mostly on the user not touching the mask once donned.) Finally, they argue that the public, lulled into a false sense of security by their masks, may neglect equally or more critical precautions such as hand washing.

Do these reasons hold true?

Each of these arguments can be challenged. The first one, for instance, is invalid on the basis that masks have been shown to be useful in other epidemics, such as SARS: the fact that they have not yet been demonstrated to be so in the context of COVID-19 does not mean that they never will. Wikipedia defines the precautionary principle as "a strategy for approaching issues of potential harm when extensive scientific knowledge on the matter is lacking." Given the rate at which the virus is spreading, coupled with the high fatality rates in specific subgroups, surely, precautionary measures are desirable at this point.

Their second argument states that masks should be reserved for healthcare workers. The solution to the inadequacy of mask supplies is to manufacture more, not withhold existing ones from a vulnerable populace. Professor Trisha Greenhalgh at the University of Oxford and colleagues hypothesize that, given the political will, existing manufacturing capacity can be repurposed to churn out any volume of masks required to provide as many as are required.

Thirdly, against a background of severe and spreading infection, the public can be easily taught to use masks consistently and properly. The final argument does not take into account the efficiency with which the public has been educated as to the danger of the COVID-19 virus. In essence, it is highly unlikely that, given an extra layer of protection, that they will neglect the preexisting ones or go to the trouble of learning how to most efficiently use both.

The masks are unlikely to be too much of a nuisance: the CDC states that they could have a "relatively small impact on social and economic life." Putting all the facts together, several researchers have independently concluded that there is no longer a need to wait for randomized controlled trials before advising the general use of masks. Given the ubiquity of the virus, the low risk of harmful effects, and the probability of benefit on plausible biological grounds, masks should be adopted by the general public even though there is no data to support their use directly.

They say, "Masks are simple, cheap, and potentially effective. We believe that worn both in the home (particularly by the person showing symptoms) and also outside the home in situations where meeting others is likely (for example, shopping, public transport), they could have a substantial impact on transmission with a relatively small impact on social and economic life."

Are cloth masks acceptable?

Almost all studies have been conducted with surgical masks: the CDC is recommending ones made of cloth. No trials have been conducted with this particular type of mask, and as such, we have a dearth of verifiable results. However, available data suggest that cloth masks may be only marginally less effective than surgical ones in blocking particle emissions, and are definitely preferable to wearing no mask at all. As the researchers say, "In conclusion, in the face of a pandemic, the search for perfect evidence may be the enemy of good policy."

However, in a related opinion piece, researchers strongly weigh in against allowing healthcare workers at any level to care for COVID-19 patients without donning proper personal protective equipment (PPE), including respiratory protection. In this situation, cloth masks are not an appropriate measure.