Subway Germs: Gross or Harmless?

For germophobes, taking the subway—with its smeared, warm railings and coughing or sneezing passengers—provokes anxiety. However, a new study provides some reassurance that taking public transit isn’t as bad as germ-conscious individuals probably believe it is.

Tiffany Hsu, one of the lead study authors and a research assistant in the Department of Biostatistics at Harvard T. H. Chan School of Public Health, told Pharmacy Times that one of the most surprising findings from the study was how hard it was to obtain DNA from the subway.

“Everyone talks about how ‘gross’ public transit is, but we actually had to collect 2 swabs per surface just to get enough DNA to sequence,” Hsu said.

She added that she was pleased to see most of the DNA they examined wasn’t associated with pathogenicity, meaning it wouldn’t cause disease in the host.

Hsu’s research looked at the Boston subway system, which takes around 238 million trips per year. The microbial communities found on the subway surfaces were mainly human skin and oral commensal microbes, such as Propionibacterium, Corynebacterium, Staphylococcus, and Streptococcus, which are normally found on humans and are harmless in most situations.

On seats and touchscreens, the researchers also found smaller amounts of oral, gut, and environmental taxa.

The FDA is currently looking into the safety and efficacy of OTC hand sanitizers, which is a product many individuals may use when they’re concerned about germs on the subway. Hsu said the short answer for whether patients should use hand sanitizers after taking public transit is: it’s complicated.

“As the CDC says, handwashing is important, especially against diarrheal and respiratory illnesses that are likely to come from bacteria and viruses in feces or other sick individuals,” she said. “Thus, it’s important to wash our hands when handling raw meat, changing a diaper, and after using the restroom, as well as when we’re around someone who is sick.”

However, she made a distinction between these activities and public transit.

“Since most of what is there seems to be microbes from healthy human skin, being on transit for a short period of time may be like shaking someone’s hand once, while being on transit for a long period of time might be like shaking multiple people’s hands,” she explained. “Shaking hands is not quite the same as handling raw meat.”

In addition, she cited some preliminary studies that demonstrate how hard it is to actually transfer bacteria between individuals’ skin.

“However, at the end of the day, we cannot rule out handwashing/hand sanitizing in public spaces such as subways, offices, or classrooms, especially during something like flu season—when it is easy to encounter someone who is sick,” she concluded.

Hsu is interested to see what the FDA finds out about antiseptic rubs and their influence on patients and microbes, since there’s some evidence that “too clean” environments may actually lead to allergies or other diseases. There’s also a possibility that these antiseptic rubs may contribute to antibiotic resistance mechanisms in bacteria.

For their next research project, Hsu and her fellow researchers plan to examine what on the subway is alive or dead. (She also credited the Massachusetts Bay Transit Authority for its help in the study with escorts and schedules.)

“I actually don't really think that differently about the subway in Boston, but now, when I ride other public transit, I’ll imagine collecting samples there,” Hsu said.