Just how effective are plastic barriers in preventing virus spread?

It's become common place these days to interact with people while a layer of plastic sits between you. 

From classrooms to workplaces, clear plastic barriers have been erected, in theory, to prevent transmission of respiratory viruses.

But how effective are they in reducing the spread of COVID-19?

A physician and researcher from Cleveland Ohio is studying just that. He says they can be beneficial, depending on the setting and type of barrier.

Dr. Curtis Donskey, a physician and hospital epidemiologist at the Louis Stokes Cleveland VA Medical Center, published a recent paper in the Cambridge University Press to report the findings of simulations he conducted using physical barriers and an aerosolized benign virus.

"The current consensus seems to be that putting up plexiglass between every student in a classroom is not likely to be very beneficial," he said on the Calgary Eyeopener.

"But plexiglass — if you are working in a store where you're seeing hundreds of customers coming through every day or in an emergency department where you know sick people are coming through and you are behind a plexiglass barrier — it may provide some protection for you in that setting."

Testing barriers

In order to put the barriers to a mock test, Donskey and his team simulated spread by spraying a live but benign version of a virus at a mannequin across a room.

They tested different types of barriers for effectiveness by recording, "whether the live virus ended up contaminating a mannequin or the tabletop where the mannequin was sitting."

"We actually saw a pretty good reduction in contamination."

Of note, when they tested barriers that had openings, like ones you might see at a convenience store — used to pass cash through for instance — they didn't work as well.

"When we used that type of barrier in our experimental setup, it was as though there was no barrier there at all … the virus moved in the air current right through the opening and contaminated the mannequin," he said.

He says that the larger a barrier is and if it is sealed leads to "a pretty good reduction in contamination."

Not a 'bullet proof shield'

Although barriers can be useful in preventing spread, they shouldn't be taken as a "bullet proof shield" given what we now know about how COVID-19 spreads, said Dr. Raj Bhardwaj, a physician and clinical associate professor at the University of Calgary.

He says that larger droplets, ejected when someone is speaking for example, can stay on surfaces and infect people but airborne transmission of the virus is still a threat.

"Those plastic barriers … might disrupt the normal airflow in a room. They might create dead zones where air becomes stagnant and those airborne viral particles can build up over time," he said.

Bhardwaj says barriers can create sometimes a "false sense of security" but they are a useful tool and that other measures like distancing, the amount of virus in a community, air circulation and proper masking need to be considered.

He adds that the "delta [variant] has evolved to be more efficiently transmissible through the air."