There's a new map of New York City's subway system, but not one you'd use to plan your morning commute; this one is a map of the bacteria and microbes found throughout the subterranean system.
The pathogen map -- dubbed by the researchers a "PathoMap" -- is mostly good news, researchers say, suggesting commuters face no risks from the tiny life forms sharing the tunnels, trains and stations of the system.
Most of the 637 identified bacterial, fungal and viral species placed on the PathoMap are non-pathogenic and are representative of normal bacteria present on human skin and in the human body, investigators from Cornell University's medical school in New York City report.
"Our data show evidence that most bacteria in these densely populated, highly trafficked transit areas are neutral to human health, and much of it is commonly found on the skin or in the gastrointestinal tract," says study senior investigator Christopher Mason, a geneticist at the university's Weill Cornell Medical College. "These bacteria may even be helpful, since they can out-compete any dangerous bacteria."
The researchers spent 18 months studying the entire system to create the first genetic profile of a metropolitan transit system, finding what was in many ways "a mirror of the people themselves who ride the subway," Mason says.
Although the new map is just a baseline assessment, repeated and ongoing sampling could yield long-term, accurate disease surveillance, bioterrorism threat mitigation, and large-scale health management strategies for New York, he suggests.
One surprise in the investigation was that about half of DNA samples collected could not be identified, and did not match that of any organisms listed by the Centers for Disease Control and Prevention or the National Center for Biotechnology Information.
Although New Yorkers come into contact with these organisms every day, until the current study they were undiscovered, and still remain unidentified.
They could represent a vast and largely untapped resource for new scientific research, Mason says.
Not all of the bacterial species detected in the subway system could be considered completely harmless, the researchers acknowledged, with around 12 percent showing some association with varieties of disease.
Live, antibiotic-resistant bacteria were found in 27 percent of the samples they collected, they noted, and two samples containing DNA fragments of Bacillus anthracis -- anthrax -- were found as were three samples containing a plasmid linked to Yersinia pestis -- Bubonic plague.
However, both were present at extremely low levels and the existence of these DNA fragments does not mean they are alive, the researchers say.
Culture experiments showed no evidence of either being alive, Mason says, and he pointed out there has not been a single case of plague in New York City since the mapping project began in 2013.
"Despite finding traces of pathogenic microbes, their presence isn't substantial enough to pose a threat to human health," he says. "The presence of these microbes and the lack of reported medical cases is truly a testament to our body's immune system, and our innate ability to continuously adapt to our environment."
