United News International (UNI) – The next time you’re on a mass public transit, you might think twice before grabbing onto the handrail.

A study published Tuesday, July 31 in Cell Reports found that passengers swap microbes — better known as germs— when they commute by subway.

Researchers from the University of Hong Kong recruited volunteers to have their palms swabbed and then ride Hong Kong’s transit system.

The researchers found people have an effect on the subway’s microbe communities.

Senior author Gianni Panagiotou said, “In the morning each line had its own microbial characteristics,” but as the day goes on, more and more human skin bacteria appear on the subways.

The researchers also examined how many antibiotics-resistant gene bacteria (ARGs) there were.

China uses more antibiotics than Hong Kong, and a subway line crossing into China had a higher number of the resistant bacteria than the other lines.

Researchers made sure to point out however, most bacteria were harmless.