What's Really Living in the Subway

Some metro systems have a reputation for being clean as a whistle. Others …I’m looking at you, New York City… have reputations for being subterranean cesspools. We get it.

With 58 billion annual rides taken, the world’s subway systems are bound to host some germs, even in the cleanest trains and stations. And in the dirty ones… it’s frightening to think about what could be festering in there.

But more than a few scientists have studied the microbial environments of subways, and they’ve made some fascinating discoveries about the differences between them. So hold on tight and stand clear of the closing doors.

You’re about to learn what’s riding along with you on the subway. [♪ INTRO] Listen, microbes are everywhere and you’re picking up a bunch when you ride the T or L or the underground or whatever you want to call it.

We know because scientists in Mexico City swabbed passengers’ hands before and after they rode the metro. By the end of a trip, the assortment of microbes they collected was more diverse than at the start. So you’re picking up quite a variety of germs.

And you’re getting them from the guy down the car picking his nose. …Or maybe from the lady who shared a section of her newspaper with you instead. Based purely on vibes, I’d rather have her bacteria all

over me. But based on science, we know that after a ride, the swabbed passengers’ microbial milieu ended up looking a lot more like their fellow commuters’ microbes. And it’s not just a Mexico City thing.

One of the most famous studies on metropolitan microbes was set in the New York City subway system: one of the oldest and busiest in the world. It’s one of only a handful of systems globally that runs 24/7, and has a long-standing reputation for being gross.

Yes, I am picking on New York, but we have a lot of Complexly staff who live in New York, and so I am saying this with love. Even the senior author of the New York study was worried about how gross it might be.

He said he was inspired to discover the microbial underbelly of the City that Never Sleeps when he caught his young daughter licking a New York City subway pole and was, understandably, concerned for her health. So he and his team got to work swabbing more

than a thousand benches, turnstiles, handrails, and other places in every single subway station in the Big Apple. They collected tiny bits of microbial DNA and then ran it through a process called sequencing. First, you identify the order of A’s, T’s, G’s, and

C’s in parts of that DNA. Then you run that sequence through a database to see if it matches known organisms. And they got more than a few matches. I’ll start with the good news: Of the top 10

most common bacterial species they found, most were bacteria usually found on skin or in soil. None of them normally cause disease in humans, although several can cause infections in people who are already sick or have had a weakened immune system.

So maybe New York City deserves a little more credit for their relatively harmless subway microbiome. But New Yorkers weren’t the only ones interested in the microscopic stowaways of their transit systems. Researchers studying the T in Boston found microbes all over

that system, too. But they noticed that the type of surface, like a hand grip versus a bench, was the biggest determinant of what kind of microbes would be there. Hanging grips close to face level had more oral microbes,

and seats had more vaginal-associated microbes. And before you raise too much concern over what goes on in Boston transit, those researchers pointed out that vaginal-associated microbes can be transmitted through clothing. So you can end up with different microbes from riding