Spreading Germs: How many bacteria are trapped by masks?

Published: Jul. 29, 2020 at 9:01 AM EDT
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ROANOKE, Va. (WDBJ) - Most places require you to wear a mask. Well, we wanted to put different types of masks to the test.

Last week, we visited Virginia-Maryland College of Veterinary Medicine to borrow an empty lab and some scientists. The two scientists who helped out had not be infected with COVID-19 and when we did the experiment, they both felt healthy, and didn’t have a fever.

The goal was to see just how many respiratory droplets a face covering catches when a person coughs, and if they’re really necessary.

For the experiment, our coughers were Peter Jobst, the director of facilities for the Virginia-Maryland College of Veterinary Medicine, and Margie Lee, the department head of biomedical sciences and pathobiology. Lee has worked in infectious diseases for 30 years.

The two suited up with gloves, while Tessa Lecuyer, a clinical microbiologist, got the Petri dishes ready to keep track of the data.

Before starting, predictions were made.

“I’m most excited to see the results of the cloth and homemade masks because I think those are most practical for most people to implement,” said Lecuyer.

“I think any face covering is going to have some positive results,” said Jobst.

“This is what I wear every day basically,” said Lee, referring to her paper mask.

The Petri dishes were then labeled.

Jobst coughed into a Petri dish without a mask first, and then with a cloth mask, followed by a gator. He also tested a face shield without a mask. Lee took on the paper mask.

“The purpose of our experiment is to see how a mask can help prevent the spread of germs from one person to another,” said Lecuyer.

But just like all good things, the results take time.

For this experiment, we left the petri dishes in an incubator for a full 48 hours. After 2 days, we were able to see how many bacteria actually grew.

The temperature of the incubator we left the dishes in was 37.9 degrees Celsius, or 98.6 Fahrenheit, the same temperature of a human body.

It takes light to see the growth, so after the wait, we headed back to the lab.

“We can see on our two samples that had no mask, we do have some bacteria on our growing,” said Lecuyer.

The surprise, however, came when we opened the petri dishes that were coughed on with face coverings.

“You can see that the plate is completely clear. It looks just like it did when we originally opened it,” said Lecuyer.

We looked at the gator sample first, but the plates for the shield, paper and cloth masks looked identical, absolutely no bacteria growth.

Side by side, you can see the difference, after just two days.

“Even for normal healthy people, there’s a lot of particles that came out of our lungs here and hit the plate, so I would say this is good for me in particular, really good proof that masks are doing what we would hope that they’d do,” said Lee.

According to Lee and Jobst, if the plates were left in the incubator for much longer, the colonies of bacteria that grew on the plate coughed on with no mask would have continued to grow, but it would have become difficult to see where the cough originated after a long period of time.

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