Broadway-Lafayette Station in New York City. (Andrew Burton/Getty Images)

Forget rats, trash and “manspreading” — the true scourges of New York’s subway system are too small to be seen with the naked eye.

A DNA examination of the city’s 466 stations revealed the transit system harbors at least 67 types of disease-causing bacteria, bubonic plague and anthrax among them. Evidence of the plague was found in three stations, while anthrax was identified on a railing and in a subway car; researchers said neither posed a threat to subway riders.

Far more common was genetic material from multi-drug resistant bacteria, such as those that cause hospital infections, which was uncovered in more than 400 stations. Other unsavory findings include the DNA of bacteria that cause food poisoning (identified in 215 stations), urinary tract infections (192 stations), meningitis and sepsis (66 stations) and staph infections (37 stations).

A rat photographed on the Times Square subway platform, in New York, Tuesday, Jan. 27, 2015. (AP Photo/Richard Drew) A rat on the Times Square subway platform. (Richard Drew/AP)

First reported in the Wall Street Journal, the survey also turned up DNA from over 15,000 more benign organisms, evidence of the system’s diverse ridership, animal, microbial and human. Researchers for the PathoMap project at the Weill Cornell Medical College painstakingly swabbed down turnstiles, benches, railings and ticket kiosks, uncovering microscopic traces of fish, rats, mice and lice. (The cockroach genome has not yet been mapped — otherwise it probably would have turned up as well.) In addition to plague and streptococcus, they also found nearly 500 types of more pleasant bacteria, including organisms that digest toxic waste such as oil and sulfates, making the city more livable. 

The human DNA samples they discovered were also telling: Analyzed for racial markers, they painted a picture of the city’s demographics that mirrors census data.

The survey even offered DNA clues into what New Yorkers are eating — mozzarella and sausage from take-out pizza, chickpeas, kimchi, sauerkraut. Weirdly, cucumber DNA was the third-most prevalent found from more complex organisms — right after that of beetles and flies, hopefully not leftovers from riders’ meals.

In an interview with the Wall Street Journal, lead author Christopher E. Mason called the project “a mirror of the people themselves who ride the subway.”

All those bacteria they found? They’re part of the reflection, too. Irrespective of hand sanitizer or frequent bathing, every human body is host to trillions of single-celled organisms not quite our own. In fact, microbial cells outnumber “human” cells 10 to one.

“You are a minority party in the democracy of the body,” Mason said.

Commuters on an L train in New York in 2014. (Lucas Jackson/Reuters)

The PathoMap results are a reflection of the messy, bacteria-infested being that is the average human. But they’re also evidence that a city is more than steel and concrete — it’s an ecosystem.

In in a report published Thursday, researchers said their findings form a “metagenomic map” of New York — the equivalent of a guide to the city’s DNA. This data will be vital for scientists seeking to understand how a built environment like a transit system impacts public health.

“Unintentionally, architects and engineers are creating ecosystems without much thought at all as to whether they are healthy or harmful to humans,” biologist Jessica Green, director of the University of Oregon’s Biology and the Built Environment Center, told the Wall Street Journal.

Green and other researchers see potential for metagenomic maps like Mason’s to help cities track disease, thwart bioterrorism and monitor changes in the urban ecoystem.

For Mason, the map is also a reminder that even an object as industrial as a subway car is teeming with life — and it’s not a bad thing.

“I want [people] to think of it the same way you’d look at a rain forest,” lead author Christopher E. Mason told the New York Times. “Be almost in awe and wonder, effectively, that there are all these species present — and that you’ve been healthy all along.”


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