Experiment by MLS faculty demonstrates effectiveness of masks and distancing

Time & Date

Friday, August 28, 2020

By Kate Hunger 

Two faculty in the Division of Medical Laboratory Science conducted an experiment to demonstrate the impact of masks and social distancing in reducing the spread of potentially contagious aerosols – including COVID-19.  Aerosols are a suspension of tiny particles or droplets in the air.

Conducted in July, the experiment was a collaboration with WOAI News 4, which reported on the results. 

Assistant Professor Terri Murphy-Sanchez, CSMLS, ASCP, interim program director of the Division of Medical Laboratory Science, set up the experiment, which included having Assistant Professor and Director of Clinical Education Cordy Kudika, MA,CHS (ABHI) speak, sneeze, sing and cough at close contact and at distances of two, four and six feet from culture plates. Kudika ran through the actions both with and without a cloth facemask.

“The bacteria growing on the culture plates are representative of the viral particles,” and have the potential of being aerosolized when people perform common activities such as talking, coughing, sneezing, and even singing, Murphy-Sanchez said.  

After 24 hours, the culture plates showed little or no bacterial growth in the trial, independent of distance when Kudika wore a mask. However, when Kudika went maskless and talked, coughed, sneezed and sang, significant bacteria growth appeared on the plates at distances of two and four feet. But at a distance of six feet, there was either no bacterial growth or minimal growth, even when Kudika did not wear a mask. The results further demonstrate the importance of maintaining social distancing from others of six feet and wearing a mask, Murphy-Sanchez said.

 “What surprised me the most is how far the droplets/aerosols travel, even when you are coughing from six feet away,” Kudika said of the maskless trial.

Both professors want the public to understand the importance of wearing a mask, particularly to prevent the spread of COVID-19 by people who are asymptomatic.

“I want San Antonians to wear masks,” Kudika said. “Wearing a mask saves people’s lives.”

Masks don’t have to be elaborate to make a difference, Murphy-Sanchez said. 

“Even a fabric, homemade barrier is better than nothing,” she said.