Researchers from Weill Cornell Medical College have spent the last 18 months scouring the New York Subway in the search for a DNA profile of the system. They even created a map of the 15,152 microbes they found.
Feb 6, 2015 Science Daily
It seems to work for the spotless Tokyo subway system, but in grimy New York? A pilot program that removed trash cans in select NYC subway stations resulted in decreased trash hauls (duh) and cleaner stations (huh). Now it's being expanded.
Sep 1, 2012 The New York Times