On the Friday before fall semester’s start, a university president and a worldwide expert on aerosol transmission of viruses sat down for a simple conversation on some complex topics related to COVID-19.

For a little more than a half an hour, Virginia Tech President Tim Sands questioned Linsey Marr, the Charles P. Lunsford Professor of Civil and Environmental Engineering, on the topics of virus mitigation strategies and the impact of the delta variant. As one of fewer than 12 worldwide experts in aerosol transimission, Marr shared valuable insights on masking and ventilation, as well as the need for individuals to assess their own personal risk factors in their day-to-day lives.

“I like to talk about it as dressing for the weather,” Marr said. “Nobody tells you what to wear, you go check the weather forecast and you decide. It’s kind of the same with the virus. Are there a lot of cases around? Is everyone vaccinated or not? Am I going to be indoors in a stuffy, poorly ventilated room for a long time or are we going to be outdoors?

“You consider all those different factors and then you say, ‘OK, do I mask or not, aside from requirements. Should I spend more time there? Should I distance?’… Unfortunately it has to become part of our daily decision-making process,” she added.

During the pandemic, Marr has been quoted dozens of times each month by global and national media outlets, has been profiled by The New York Times, and has amassed more than 48,000 followers on Twitter, where she regularly fields questions from the public.

“I’m so impressed with the tone you have when you answer those questions,” Sands said. “Obviously, you know what you’re talking about, but where you don’t know, you find out and when something changes, you adjust your guidance. And I also admire the fact that you meet people where they are … and you related it to your own experiences. Those are all things that make for effective communications in a pandemic.”

Throughout their conversation, Marr shared guidance to aid Hokies in making the best decisions for themselves and their communities during the upcoming semester and football season. She encouraged the Virginia Tech community to embrace the chance to be a model during this time.

“I think we have an opportunity here to be an example of good policies and responsible behavior to help bring this pandemic to an end as soon as possible,” Marr said.

Vaccine mandates and indoor masking requirements

Earlier in the week, Virginia Tech announced COVID-19 vaccines would be required for all university employees with the exception of those with medical reasons and sincerely held religious beliefs. This came shortly after the announcements of a requirement for face coverings in public indoor spaces and a surveillance testing program. Students were already required to be vaccinated.

Sands asked Marr for her thoughts on the recent requirements amidst the rising COVID-19 case numbers and the highly contagious delta variant.

Marr said from a global perspective, countries had run into trouble when they either didn’t push vaccines enough or thought, because of vaccines, they could relax mitigation efforts.

“What we’ve learned, especially with delta now, is that we need to be strong on both fronts,” Marr said. “I think that’s why Virginia Tech’s vaccine mandate and the requirement for indoor masking right now makes a lot of sense until we get past this next hump.”

She pointed out that while vaccinations have proven very effective at preventing hospitalization and death, they were not meant to prevent simple cold symptoms. And the highly transmissible nature of the delta variant meant even more vaccinated people could catch it, and more importantly, spread it to vulnerable or unvaccinated people.

“If we didn’t have masks, you could easily have some kind of outbreak where people got infected without having severe symptoms of disease,” Marr said. “But then all those people are contagious…and it seeds more infections. At Virginia Tech, we don’t want to be that seed that’s setting off more infections with all the people we’re connected with.”

On the best masks

“I think with delta it’s more important than ever to think about the performance of your mask,” Marr said.

She said the keys to a good mask are fit and filtration. It is important to check for leaks around the nose, chin, and cheeks, and to consider upgrading to a mask with a filter or double-mask with a surgical mask covered by a tight-fitting cloth mask.

On face shields and plexiglass

Marr said both mitigation methods were considered to be effective when it was commonly thought COVID-19 was mostly spread via larger droplets. They are far less effective in preventing the much smaller aerosol transmission, which is now the primary vector for spread. She compared both method’s effectiveness in preventing COVID-19 infections to how well they would perform in blocking cigarette smoke.

“Imagine you’re in a room filled with cigarette smoke. Is that face shield going to protect you? No, it [the smoke] is going to go around the face shield,” Marr said.

Marr added that the larger barriers could actually prevent airflow in indoor spaces and put people more at risk.

On ventilation

“We can’t see the ventilation … but that’s what’s going to make a bigger difference than barriers or face shields,” Marr said.

Marr said she’d been in contact with Virginia Tech’s facilities team and was impressed with the work they had done on campus. That includes bringing in more outdoor air, using better filters, and adding standalone air purifiers in some older classrooms.

“I think they’re doing all the right things in terms of ventilation,” she said.

On football games

Lane Stadium plans to welcome fans for the first time since 2019 this fall. Though outdoors, Marr said individuals should consider the vaccination status of those they are sitting near when deciding what precautions to take in the stands.

“I would probably wear a mask because you’re there for two or three hours at a time. You’re close, and people are loud and shouting,” she said.

Marr said her general rule of thumb for outdoor activities is to mask when she’s close enough to repeatedly touch other people.

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