Scientist reveals how masks stop coronavirus from spreading in viral photos

‘Masks keep your respiratory secretions to yourself,’ writes Dr Richard Davis

Olivia Petter
Tuesday 14 July 2020 09:00
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Significant numbers from the coronavirus lockdown

A microbiologist has demonstrated the effectiveness of wearing a mask in preventing the spread of Covid-19 in a viral Twitter thread.

Dr Richard Davis posted photographs of an experiment he conducted to illustrate exactly how wearing a face mask blocks germs from transmitting between two people.

“What does a mask do? Blocks respiratory droplets coming from your mouth and throat,” he tweeted.

“Two simple demos: First, I sneezed, sang, talked & coughed toward an agar culture plate with or without a mask.

“Bacteria colonies show where droplets landed. A mask blocks virtually all of them.”

The difference, as illustrated by the different petri dishes in the photo, is enormous; there are virtually no germs in the dishes used when Dr Davis was wearing a mask, and plenty of germs in the ones used when he was not.

In a second demonstration, Dr Davis showed how effective social distancing can be both with and without a mask.

“I set open bacteria culture plates two, four, and six feet away and coughed (hard) for ~15s,” he tweeted.

“I repeated this without a mask. As seen by number of bacteria colonies, droplets mostly landed <6 ft, but a mask blocked nearly all of them.”

The photos once again illustrated the profound impact that wearing a mask has on preventing the spreading of germs.

Dr Davis added that he was aware his experience isn’t how you would typically model the spread of the coronavirus, but that it still showed the effectiveness of face masks and coverings in stopping the spread of the illness.

“I’m aware that this simple (n=1) demo isn’t how you culture viruses or model spread of SARS-CoV-2,” he wrote.

“But colonies of normal bacteria from my mouth/throat show the spread of large respiratory droplets, like the kind we think mostly spread #COVID19, and how a mask can block them!

In England, it is now compulsory to wear a face covering while using public transport, and is expected to become compulsory in shops from 24 July.

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