US dollar bills from New York City house over 3,000 bacteria, some found on human hands, mouths, and even vaginas, ABC News reported.
"We're not trying to be fear mongers, or suggest that everyone goes out and microwave their money," biologist Jane Carlton, who's leading the Dirty Money Project at the New York University, told NPR. "But I must admit that some of the $1 bills in New York City are really nasty."
The project offers an in-depth look at the living organisms infesting our currency, hopefully providing useful information that could help health workers catch disease outbreaks in New York City before they spread.
So far, Carlton and her colleagues have sequenced the DNA found on about 80 one-dollar bills from a Manhattan bank. They found the most common microbes on the bills were harmless ones that caused acne, followed by several non-pathogenic skin bacteria. Some microbes present even originate in the mouth - most likely, researchers speculate, from finger-licking bill counting - and the vagina.
But more importantly, the DNA detected antibiotic resistant genes that make bacteria impervious to penicillin and methicillin - the latter used to treat MRSA, a bacterium responsible for several difficult-to-treat infections in humans.
"Now we know that viable bacteria are on money and could serve as a mode of transmission for antibiotic-resistant genes," Carlton said. "Money is a frequent route of contact between people in New York City."
Researchers also found the flu virus was prevalent on the tested money, especially in the wintertime during flu season. This suggests the money inhabiting your wallet could spread contagions. But NYU biologists said there is no reason to overreact.
"Microbes are so important, are very ubiquitous and they surround us all the time," Carlton told ABC News.
A possible solution could be changing the material money is made from. Canada has started printing their money on polymer film, a fancy plastic, which supposedly provides a less bacteria-prone environment, NPR reported.