COVID-19 is spread primarily through the respiratory droplets that we expel when we talk, cough, sneeze, and breathe. Transmission happens when pathogens are enveloped in these droplets and they land on an uninfected person. These droplets have been responsible for the transmission of various other viral and bacterial illnesses including influenza, tuberculosis, and SARS.
The SARS outbreak is one of the key reasons that face masks are widely worn in Asian countries. Face masks reduce the risk of a person infected with COVID-19 from spreading it to a healthy person, by minimizing the spread of droplets released when we cough or sneeze. The efficacy of face coverings has been widely debated in the US, but multiple studies have, in fact, proven that masks reduce the risk of transmission of COVID-19.
Numerous reports have been published on the efficacy of medical-grade face masks, but there haven't been any clear guidelines on which materials and designs are most effective for face masks. In particular, specific data is sparse on the cloth masks that most of us use.
New Research on the Efficacy of Masks
New research from Florida Atlantic University’s College of Engineering and Computer Science has recently been published in Physics of Fluids and is demonstrating a new method to assess the effectiveness of masks. This research uses visualizations using imitation coughs and sneezes to discover how well droplets are blocked.
Researchers in the lab used a technique called flow visualization to collect data on mask efficacy. A synthetic fog was created using a combination of glycerin and distilled water. Masks were placed over a mannequin’s mouth and the mixture was sprayed from its mouth to simulate a sneeze or a cough.
This test was performed using a variety of masks that we, the general public, have access to, with the purpose of mapping the path of escaped droplets to see how each mask performed. The test was conducted on a bandana-style covering, a homemade mask using two layers of cotton, and a non-sterile cone style cloth mask like the ones sold by Carii Wear. Medical grade masks and respirators that should be reserved for front-line healthcare workers were not tested.
What did the Tests Reveal?
The test showed that using a bandana to cover your nose and mouth does offer some protection against potentially infecting others in your community by reducing spread to less than four feet. However, homemade masks and professionally manufactured cloth masks were shown to be much more effective at stopping the spread of aerosolized droplets from the mannequin. They reduced the spray distance to 2.5 inches and 8 inches respectively. Although some leakage was noted through the mask and around the edges, both of these mask designs were proven to effectively reduce the speed and range of respiratory spray that could potentially spread coronavirus.
Researchers also conducted the test without using a mask, and the imitation coughs traveled much further than with any of the coverings. In fact, the range was larger than the current 6-foot social distancing guidelines published by the US Centers for Disease Control and Prevention (CDC). Spread was recorded up to 12 feet away from the mannequin in just 50 seconds, which clearly shows the dangers of entering any public spaces without using a mask. Researchers also noted that tracer droplets remained suspended for as long as 3 minutes.
How to Effectively Prevent the Spread of COVID-19
Siddhartha Verma, ph.D. the lead author of the paper, said, “In addition to providing an initial indication of the effectiveness of protective equipment, the visuals used in our study can help convey to the general public the rationale behind social-distancing guidelines and recommendations for using facemasks.”
Dr. Verma pointed out that it is critical to promote widespread awareness of how to effectively prevent the spread of COVID-19. This warning comes at a time that many places across the US are observing spikes in cases. Florida, in particular, is seeing a drastic rise in cases. At the time of publishing, the state has seen 169,000 confirmed cases and 3,616 deaths.
The results of this study suggest that current social distancing guidelines may need to be updated to account for the wider spread of droplets by those that aren’t wearing masks in public spaces. They also prove that wearing a face-covering can help ensure that infected people don’t unintentionally spread COVID-19 to those around them.