Masks could be more effective than earlier thought, blocking up to 99.9% of COVID-19 laden droplets released by infected patients and carriers, according to a new study by the Roslin Institute at the University of Edinburgh.
Containing the spread of COVID-19 has been a tricky task. It is one of the main reasons why COVID-19 quickly spiralled out of control and became a pandemic. As an increasing number of countries mandate the use of facial coverings in public spaces, scepticism surrounding their benefits has permeated the minds of the general public.
Are masks effective? Do they work?
One concern about the spread of COVID-19 was how pre-symptomatic patients could potentially serve as carriers, spreading the virus through droplets emitted by coughing, sneezing, and even speaking. This has made tracing the sources and spread of the virus very challenging.
A research team from the Roslin Institute at the University of Edinburgh have shown that masks could help. According to their new study, masks can block 99.9% of COVID-19 laden respiratory droplets from infected people.
The team tested the efficacy of surgical masks and the basic single-layer cotton masks that are recommended for use by the general public. They used a life-sized anatomical human model connected to a machine that simulates coughing and speech, to release fluorescent droplets mimicking respiratory droplets. Using in-flight laser sheet illumination and UV-light, they could track and count the fluorescent droplets that landed on a 2 metre high surface in front of the person.
Pre-symptomatic patients could potentially serve as carriers, spreading the virus through droplets emitted by coughing, sneezing, and even speaking.
To check if these results were robust in a real life setting, they carried out further tests on human volunteers, with and without masks. They used a microscopic slide to determine the spread of respiratory droplets released in speaking and coughing conditions.
In both the model and in people, the masks worked. The number of respiratory droplets expirated were more than 1000 times lower, even when the facial covering was a basic single-layer cotton mask. Surgical masks were determined to be slightly more effective, as the team found that in simulations with surgical masks, zero particles were released.
These results contrasted with prior studies, which deemed masks less effective in blocking the spread of the virus. However, these studies also took into account smaller sized droplets. These droplets, called aerosols, are expirated and can remain airborne for several hours.
Masks can block 99.9% of COVID-19 laden respiratory droplets from infected people.
It remains uncertain how much viral transmission occurs by aerosol. The team has cautioned that the study could potentially be overestimating the protective effects of face masks if aerosols are significant drivers of COVID-19 transmission within the public.
Nonetheless, the bigger droplets carry higher loads of the virus. By blocking them, masks could be quite useful in reducing spread to immediate surroundings. Even with aerosol transmission, masks could still be quite effective if used in addition to stringent social distancing measures together with better ventilation.
“We knew face masks of various materials are effective to a different extent in filtering small droplets. However, when we looked specifically at those larger droplets that are thought to be the most dangerous, we discovered that even the simplest handmade single-layer cotton mask is tremendously effective. Therefore, wearing a face mask can really make a difference.” says lead researcher Dr Ignazio Maria Viola, from the University of Edinburgh’s School of Engineering.
Moreover, the results of the study could have implications on social distancing norms. Currently, social distancing restrictions necessitate a distance of two metres (six feet) to be maintained. The team found that someone standing two metres from a coughing person without a mask is exposed to 10,000 times more droplets than someone half a metre from a coughing person who is wearing one.
“We looked specifically at those larger droplets that are thought to be the most dangerous, we discovered that even the simplest handmade single-layer cotton mask is tremendously effective.”
– Dr Ignazio Maria Viola, from the University of Edinburgh’s School of Engineering
Many businesses have been affected by social distancing norms as is. It has been hard to strike a balance between supporting the economy and public healthcare simultaneously. This study, although yet to be peer-reviewed, provides concrete evidence that masks could help reduce the spread of COVID-19 as businesses and social lives slowly return to normal.
“The simple message from our research is that face masks work. Wearing a face covering will reduce the probability that someone unknowingly infected with the virus will pass it on.” says Professor Paul Digard, the Chair of Virology at the University of Edinburgh, who was a part of the research group at the Roslin Institute.
Written by Simran Kapoor and edited by Tara Wagner-Gamble.
Simran’s thoughts… The world has become divided on the topic of face masks. Growing scientific research is providing evidence in support of the benefits of wearing face masks to contain the spread of COVID-19. It is, indeed, a low cost (albeit slightly uncomfortable) way to help reduce the chances of spread. Yet, many people remain reluctant about using masks. A lot of the spread could be coming from pre-symptomatic carriers or those with mild symptoms. They are likely to be completely unaware that they have the virus and hence don’t wear masks. Others believe wearing masks is an infringement of their freedom. But these kinds of thoughts could be having dire consequences. It is quite true that a false sense of security may prevail among people wearing masks and create a risk of spread. But in my opinion, this should not become a reason to avoid masks. Instead, more efforts must be made to educate people on how masks must be worn and why they must be worn to dispel these myths. Disinformation is especially dangerous right now and risks putting all the efforts so far to waste. The pandemic has not gone away, and we must take every precaution we can to save lives. The delay in reaching this consensus is worrying and it is likely to lead to more deaths. Social distancing and wearing masks have no negative consequences. If these measures are adopted correctly, they can only help while we wait for a vaccine.
Simran Kapoor is a 4th year Biological Sciences student with an interest in molecular biology, immunology, and infectious diseases. Find her on LinkedIn @Siman Kapoor.
