Which Bugs Are Hitching a Ride on This Subway?

General Health
Source: Boston.com

The subway is famous for many things, many of them unpleasant. The New York City subway, for example, is notorious for its disgusting rat population.

If you’ve ever ridden the NYC subway, you know you can’t stand on a subway platform without seeing at least one rat run by. Some of those suckers are as big as a purse or a carry-on bag. Maybe you remember Pizza Rat, the infamous rodent seen dragging a huge slice of pizza down the NYC subway stairs.

Subway rats carry fleas capable of harboring bubonic plague, parasites, and a host of other potentially deadly bugs.

Although the NYC subway is most notorious for its filth and vermin, the problem certainly isn’t unique to that city.

Recently, scientists set out to discover which shudder-worthy germs accompany riders on Boston’s subway, and they uncovered mostly good news.

The Boston subway, a.k.a, the Boston T, dates back to 1897 and is the nation’s oldest subway system. Today, it’s among one of the most crowded systems in the world, making some 238 million trips every year, running under Boston Harbor and branching out to suburbs like Brookline and Newton.

In 2014, the Boston T shuttled 400 million people back and forth.

That’s a lot of people wiping their noses on their sleeve, coughing into their hands, and then touching the same handles, seats, and doors.


Microbes Lurking in Boston Subway

Researcher Curtis Huttenhower said he first became interested in what microbes might lurk in the Boston subway after reading about other work being done to analyze bacteria in “built” or human-made spaces.

The materials and chemistry of these “built” places differ greatly from those found in nature, and the life in these environments is greatly influenced by microbes that live on humans.

Humans are surrounded by their own bacterial cloud that is as unique as a fingerprint. People leave traces of their clouds everywhere they go, and when they’re in close proximity to others, these clouds mix together to create a somewhat germy “soup.”

Huttenhower told The Washington Post:

“I wanted to take a look at the subway because of the link to the human microbiome. It’s a place where thousands and thousands of people interact every day and it can be thought of as a conduit or reservoir for human microbes getting from one person to another.”

For three days, Huttenhower and his colleagues rode the Boston T and took swabs from seats, seat backs, vertical and horizontal poles, hanging grips, and walls inside 15 train cars on the red, orange, and green lines, plus swabs from touchscreens and the walls of ticketing machines in five stations.

The researchers carried out their work during the spring and fall to get a baseline reading that was less influenced by people being bundled up against the cold, or sweating in summer’s heat and humidity.

The investigators also found few anti-microbial-resistant bugs. In fact, they found a minimal number of microbes capable of causing illness. No anthrax or bubonic plague.

Read: First Case of the Plague in the United States for 2016

It’s reassuring that few antimicrobial-resistant bugs were discovered, considering that a bug resistant to all drugs, including last-resort antibiotics, was recently detected in the United States, and that researchers believe it has been here for several years.

  • The majority of the bacteria found on the Boston T came from normal human skin, the mouth, gut, and other places in the body that will make you want to live in a bubble.
  • Lachnospiraceae, Veillonella, and Prevotella from the gut were found in low proportions.
  • Vaginal microbes – which can be transferred through clothing – were also found on some of the seats.
  • Additionally, non-human microbes were discovered,. These included Alphaproteobacteria, a class of bacteria that exists mostly on plants, and Sphingomonads, found in soils and sediments. Most of these were found on outdoor touch screens.

Huttenhower said:

“The vast majority of the bugs you encounter in the subway that is thought of as a germy kind of place you’d encounter shaking someone’s hand. You’d want to wash your hands, but it’s not something that’s more scary or dangerous.”

However, Huttenhower admitted that it’s more like shaking thousands of hands every day.

He explained that it was hard for the researchers to determine which bacteria were deposited, dormant, or actively growing. In the coming months, the team will return to the Boston T to take more swabs to examine that question.

Huttenhower’s team also plans to examine changes in the microorganism mix during flu season, when more highly infective bugs are likely to be present.

Only two other studies have examined the microbes existing in subway systems – one was conducted in New York City, the other in Hong Kong.

The authors of the New York City study initially said they’d actually found anthrax and bubonic plague on the subway, but later revised those findings. The confusion surrounding the study was part of the inspiration behind Huttenhower’s research.

The findings of the Boston T study could help researchers monitor the microbial composition of subway surfaces, and use it as a way to tell whether flu symptoms are increasing.

Huttenhower told the Los Angeles Times:

“If we know what the baseline microbial profile looks like, then a change in that profile, or the sudden detection of a pathogen could provide an early notification that something is going on.”

The study can be found in the open access journal of the American Society for Microbiology.

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