How Viruses Spread: Q&A With Jordan Peccia

Jordan Peccia, who focuses on human exposure to environmental microbes, recently studied the microbial communities on students’ desks in a Connecticut school district. He and his research team found that the bacteria and fungi overwhelmingly came from the hands, mouths, and gut of children sitting at the desks. They also found that, even after a desk cleaning, the microbes were back in full force within a few days.

We spoke with Peccia, the Thomas E. Golden, Jr. Professor of Chemical & Environmental Engineering, about the need to study where harmful microbes are, how they transmit from one person to another and how the Covid-19 could change long-term perceptions about respiratory illnesses.

How did the school desk study come about?

As part of a study to figure out how to make them healthier places, Lysol was interested in a pilot effort to see if we could track respiratory and gastro intestinal viruses on school desks. In the first five months of 2019, our team took over 300 desk swab sample in six second, third, and fourth grade classrooms in a Colorado school district.  We found rhinovirus, adenovirus, norovirus, and coronavirus. 

Not the coronavirus that’s spreading now, right?

Right - this was Coronavirus OC43. The big one we’re worried about now is called SARS-CoV-2 or “Covid-19”. Prior to the emergence of SARS in 2002, MERS in 2012, and the current COVID-19 strain, there were and continue to be four other strains of Coronavirus that commonly infect humans. These four have been circulating around forever and they account for 15% to 20% of colds every year. In general, and during the cold and flu season, about 20% of the desks we encountered had detectable levels of respiratory virus on it. And If you change desks every day for different classes, that number balloons to a 70% chance of encountering a desk with respiratory viruses.

So the question then is, why isn’t everyone getting sick? Number one, as any parent can attest, they are getting sick a lot in school. Number two, sitting at a contaminated desk or touching a doorknob doesn't necessarily mean you’re going to become infected. The virus has to run a gauntlet of occurrences to infect. One would first have to touch the desk, pick up an infectious dose, then touch your mouth, nose, or eyes - all of these things have to happen for you to get sick. While this necessary series of occurrences protects us,  you can see why schools or other high occupancy environments, especially if things aren’t continuously disinfected, are good at transmitting disease. 

As for social distancing, how does the 6-foot rule work?

There’s a couple ways respiratory diseases can be transmitted. They key example is direct contact which includes droplet spread.  For example, if I have the virus and cough, sneeze or talk and emitted droplets land on or in someone’s mouth or eye or hand. The rule suggests that six feet is beyond the firing range of our oral or nasal projectiles. As airborne particles go, droplets are big and they'll fall to the ground before they travel six feet. Everything that we can cough and sneeze out should have made it to the ground by then. 

The indirect contact route however, has less respect for time or space. For example, let’s say a student comes to visit me for office hours. He’s sick and sneezes into his hand and then uses a doorknob on his way out. Later that day, I leave for home, open the door, use the elevator button and rub my eye. This just one of the ways that surfaces can transmit disease.

Would an increased public awareness about microbes help diminish the way they spread?

Yes. It's strange because until something like Covid-19 happens, many Americans have thought of respiratory viruses as a nuisance you have to deal with - I've never thought of them that way because I study how to eliminate transmission. 

Across the U.S., there are very few infections each year from drinking water and no one drinks water and expects to get gastrointestinal illness - if we did, we’d call it an outbreak and bemoan our nation’s crumbling infrastructure. But we’ve all somehow talked ourselves into thinking that it's OK to get three to five respiratory infections a year- more if you’re a child. So it’s not completely surprising to me that there’s never been an extensive survey of just what kinds of viruses are on certain public surfaces. My lab hopes to continue to understand the occurrence of viruses on public surfaces - subways, railings, doorknobs, you name it, in busy urban areas around the world. Once we know this better, we’ll be able to recognize high-risk surfaces that are target areas for cleaning. Not just during a pandemic, but to reduce the overall incidence of respiratory infections transmitted in the built environment.