Grabbing a handrail on the New York subway transfers as much bacteria as shaking hands with 10,000 people. That’s according to a recent study that found the Big Apple has by far the most bacteria in its subway system compared with other US cities. Many of the bacteria founds have been known to cause respiratory problems and skin infections, although scientists stress most are harmless and could even be good for our immune system.
Travelmath, a logistics website, sent a team to gather bacteria samples from public transit systems in five major cities: New York, Washington, D.C., Chicago, Boston, and San Francisco.The study found that while ‘surprisingly few germs’ were on handrails on most cities, there was one major exception: New York. The Big Apple’s subway system has more than three times as many travelers as the city’s other four transit systems combined.
The team found to have an average of two million colony-forming units (CFU) per square inch. CNTraveler notes that this is 900 times dirtier than an airplane tray table. On the other end of the spectrum was the subway in Boston, with a sample that turned up a scant average of about 10 CFU per square inch.
Bay Area Rapid Transit in San Francisco was the second grubbiest subway, with 483 CFU per square inch; the Chicago ‘L’ train was third with 180; and the Washington, D.C. Metro turned up only 30. The average for every city’s transit system was about 400,000 CFU per square inch, though excluding the bacteria-ridden New York subway dropped the average to 176 CFU. ‘We dug deeper to break down the bacteria we found by type: Bacillus, yeast, and various gram-positive and gram-negative strains,’
TravelMath writes on its blog. ‘The subway in New York contained an even split of gram-negative rods (which can cause respiratory and other infections) and yeast (types of which commonly live on skin and rarely cause infection).
‘The L train in Chicago was home to the most varied bacteria types, the brunt of which were yeast. ‘BART in San Francisco and the Metro in Washington, D.C. both predominantly hosted gram-positive cocci, which are a common cause of skin infections.’The Metro was the only location that yielded type II gram-positive cocci, and only BART and the L-train contained Bacillus, which can cause a range of infections, including respiratory illnesses.
‘Our samples from the Boston subway, home to the fewest bacteria, didn’t reveal any specific types,’ TravelMath writes. The firm is quick to point out that not all of this bacteria is dangerous. In fact, studies have shown that exposing people to different types of bacteria boosts their immune system.
The study follow similar research done last year by scientists from Weill Cornell Medical College. They spent 18 months swabbing turnstiles, ticket kiosks, railings and benches for DNA in New York.
They found 15,152 different types of microorganisms that share the train with its 5.5 million riders. At the time they linked these to bubonic plague, anthrax and meningitis – but the scientists have since retracted these claims.
Principal Investigator Dr Chris Mason and his team released findings from their ‘PathoMap’ study, a map of all the microorganisms and DNA present on surfaces in the New York City subway. The study, which used a super computer to study more than 10 billion biomedical fragments, was apparently inspired by Dr Mason seeing his daughter, then in preschool, sticking toys in her mouth in 2010.
Scientists and volunteers started the project in 2013 and found 637 known bacterial, viral, fungal and animal species when swabbing the spaces between commuters and street musicians and logging the data in real time with a mobile app. Most of the bacteria the group found were harmless, though nearly half (48 per cent) of the DNA found matched no known organisms, according to the published study at Cell.com. The mysterious finding ‘underscores the vast wealth of unknown species that are ubiquitous in urban areas,’ project leader Ebrahim Afshinnekoo said.
Researchers also saw 67 different bacteria species associated with diseases on the subway’s surfaces in about 12 per cent of their samples, though bacteria in general made up nearly 47 per cent. Some bacteria associated with ailments such as food poisoning are found at nearly half of the 466 open stations shared by germs, riders and rats.
Thankfully, more serious bacteria are less common. The New York City Department of Health disputed the finding of plague on the subway, according to the Wall Street Journal. The most diverse station was the G train’s Myrtle-Willoughby stop in Brooklyn, with 95 different bacteria groups. South Ferry station, which was submerged and temporarily closed after Superstorm Sandy in 2012, showed unique sets of bacteria normally found in marine environments.