To understand why the MacArthur Foundation singled out Linsey Marr for one of this year's fellowships – the so-called "genius grants" – you have to go back to the first days of the COVID-19 pandemic and recall how uncertain everything was. The early guidance from health experts emphasized washing hands and keeping six feet from others with no recommendation to wear masks or avoid gathering indoors.

Linsey Marr, an aerosols expert and professor of civil and environmental engineering at Virginia Tech, became convinced that advice was based on a flawed idea of how respiratory viruses spread. Her groundbreaking research and tireless advocacy showed that the virus is airborne as opposed to traveling in large droplets that fall with gravity.

That work helped lead to a course correction in the public health guidelines and likely saved lives. Current guidance emphasizes that the virus can travel much farther than six feet. The EPA advises, "particles from an infected person can move throughout an entire room or indoor space. The particles can also linger in the air after a person has left the room – they can remain airborne for hours in some cases."

NPR caught up with Marr, one of 20 individuals honored by the MacArthur Foundation this year, to learn about her pandemic journey and why she believes clean air is inextricably linked to our overall health. The interview has been edited for length and clarity.

Can we recap the early pandemic from your perspective? What do you remember from those first days when the authorities were still figuring out how to talk about it?

I remember in December 2019 and January 2020 hearing about the new virus spreading in China. And I remember reading a story in The New York Times where they said, oh, the virus only travels up to six feet. On the other hand, other viruses like measles or chickenpox can travel much farther. And I remember thinking to myself – and tweeting – but why? This is wrong.

I knew that conventional wisdom was that colds and flus were spread by large droplets that people cough out of their mouths and they fly through the air like mini-cannonballs and land on someone else's nose or mouth. And then that's how the other person gets infected. And I became more and more concerned that officials were really missing out on a major mode of transmission, and that if we didn't address it, we were not going to be successful in trying to control the virus.

Can you explain the difference between these two different modes of transmission – droplet versus aerosol? Why is it such an important distinction?

When people talk or cough, they emit those large, visible, wet droplets, but they also emit thousands of tiny particles that we can't see and these can also carry the virus. They stay suspended in the air, and they can float around for a while. The particles end up depositing on the inside of your nose or along your respiratory tract, get down into your lungs, and they cause infection.

The other way that transmission can occur, in theory, is through spray of large droplets. Those can travel maybe up to six feet. In some rare cases they can go farther, but they're going to fall to the ground within seconds. And if you keep your distance, then they will not land on you.

And the distinction is really important because it defines how we would prevent transmission. If the virus is being transmitted through inhalation of these tiny particles in the air, then we need really good filters or masks or ventilation to block these particles. If you tell everyone to maintain their distance of six feet, that's not going to work because those tiny particles can easily travel more than six feet, and you can breathe them in at a distance.

What do you think this pandemic paradigm shift says about the importance of working across disciplines on these gigantic problems?

For the pandemic, everyone looked to medical doctors and public health officials for guidance, and they certainly have expertise in what's happening with the virus when it's in your body and what we can do about it on a population scale. But I think they were not savvy to what we can do in the indoor environment to reduce the risk of transmission, because they weren't really aware of the mechanics of transmission. And that's where aerosol scientists and engineers can play a role. But we were shut out of the discussion because it was thought that our expertise wasn't relevant.

I think the pandemic really raised our awareness about the importance of and the consequence of the air we breathe when we're indoors. Because when people say the word air pollution, they typically think of outdoor air pollution – factories or power plants belching smoke into the air. And so if we think about the virus as a pollutant, as a particle in the air just like other particulate air pollution, then we have a huge body of knowledge that we can apply to this problem.

What do you recollect about what this period was like for you personally in those first few months? Did you feel like a voice in the wilderness?

I was stressed about the wrong messaging coming across and knowing that so few people in the world really understood how transmission physically happens. And I felt that it was important for me to speak up about it. Then the number of interviews rapidly escalated, and then over the summer it got to the point where I was doing 10 interviews a week and we were turning down a lot more. I was being consulted by various public health agencies, and I was asked to review some reports for the White House from the National Academies and turn it around within hours. It was exciting to be living my research in a way, but also stressful, of course, knowing that this was leading to suffering and death.

What has it been like to get this recognition? Did you ever expect to be a star?

No, no, not at all! It never crossed my mind. I feel like I won the golden ticket in Charlie and the Chocolate Factory. So I have a lot of mixed feelings – mostly good, but I also feel the weight of expectations on me. I'm just trying to do my work, answer interesting questions, do a good job at it – and then the pandemic came along. When I first started working on [airborne virus transmission] 15 years ago, I knew it was going to be a big deal because it was very clear to me that the conventional wisdom conflicted with physics [of how particles move in the air] and just was not possible. But I thought it would be, oh, maybe 30 years from now, people will finally figure this out.

And I guess it also put on display how changing these paradigms requires tenacity and some courage. That seems to be part of your story, too.

You know, I worked on this problem that was really not recognized in any particular discipline. And so I felt like an outlier when I presented at conferences. Nobody else was talking about anything like this. Or I submit papers to journals that get rejected because it didn't fit in any predefined discipline, and I'm sure people were wondering, what are you doing and why are you working on this? But to me it was a really interesting question that I was convinced would be important. And so now it turned out to be very important – sooner than I thought.