How many parents, seeing their toddlers place some filthy toy in their mouths, feel a shiver of disgust when they consider the countless dirty surfaces one brightly colored plastic object most likely touched? Interestingly, this instinctive reaction served as inspiration for a new study from researchers at Weill Cornell Medical College. PathoMap, the brainchild of scientist and father Dr. Christopher Mason, paints a molecular portrait of the New York City subway system, which he says contains 637 known bacterial, viral, fungal, and animal species, plus an equal number of unknown organisms.

While the researchers characterize most of the microbes as harmless, they acknowledged the subway is also home to disease-causing — and drug-resistant — bacteria, with an added dollop of DNA fragments linked to anthrax and Bubonic plague. Before anyone boards the first flight back to Kansas, Mason says his crew found only very low levels of these DNA fragments and none showed any evidence of being alive in the culture experiments he performed.

“These data indicate that the subway, in general, is primarily a safe surface,” the researchers wrote in their published study.

In fact, most of the known bacterial, viral, fungal, and animal species detected in the subway represent normal bacteria present on human skin and human body. In other words, they are were non-pathogenic. However, nearly 12 percent of the sampled bacteria species showed some link to disease. Live, antibiotic-resistant bacteria were present in 27 percent of the samples. Plus two samples contained DNA fragments of Bacillus anthracis (anthrax), and three samples contained a plasmid connected to Yersinia pestis (Bubonic plague).  Mason repeats, none of these fragments showed signs of life.

Apparently, these virulent organisms are simple co-habitants in the shared city and do not foreshadow widespread sickness or disease. Still, Mason and his co-authors noted “wider testing is needed to determine how common this is in other cities.”

Launched in 2013, PathoMap had two core objectives. First, Mason and his colleagues simply wanted to map the microbiome (the entire collection of all microorganisms) and DNA present on the surfaces of a city. Second, once they’d established this baseline, they hoped to continue monitoring the pathogens, essentially creating a series of subsequent maps and sending alerts whenever a potential outbreak is detected. In this way, the scientists might construct a long-term narrative about the dynamics and health of one urban environment at a precise, molecular level.

Source: Afshinnekoo E, Meydan C, Chowdhury S, et al. Geospatial Resolution of Human and Bacterial Diversity with City-Scale Metagenomics. Cell Systems. 2015.