In the first comprehensive study of genetic material found on dollar bills, researchers discovered that cash carries on its surface an average of nearly 3,000 kinds of bacteria, The Wall Street Journal reported.

Scientists at New York University’s Dirty Money Project say this is many times more than researchers previously found when they inspected the bills under a simple microscope.

For the latest experiment, NYU scientists computer-analyzed the DNA found on 80 $1 bills they collected last year from a Manhattan bank. About half of the genes they found were human. In addition, researchers also found bacteria, viruses, fungi and plant pathogens on the cash. “We actually found that microbes grow on money,” said Jane Carlton, PhD, a professor of biology and the director of genome sequencing at NYU’s Center for Genomics and Systems Biology.

By far, the most common species of bacteria found on bills was one that causes acne. Other pathogens were linked to stomach ulcers, pneumonia, food poisoning, staph infections and even antibiotic resistance. Interestingly, researchers also found minute traces of anthrax, diphtheria and white rhino DNA embedded in the bills.

The still unpublished study sheds light on the growing debate about the health risks of distributing frequently handled paper money. Many public health experts view the notes as a potentially serious source of contagion.

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