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Money really is dirty: Circulating bills and coins contaminated with pathogens

Many of us remember our mothers telling us to wash our hands after handling money: "You don't know where that money has been, or who touched it last!" "Money is the dirtiest thing in the world!"

Wash your hands! You don't know where those coins have been.
Photo by Clive Rose/Getty Images

Well, the Allentown Family Health Examiner doesn't know if it's the dirtiest thing in the world, but money certainly does carry its share of pathogens. Researchers from the University of Buea in Cameroon, Africa, have just published a paper demonstrating that circulating currency carries bacteria such as Staphylococcus aureus and fungi such as Aspergillus sp. Nearly 97 percent of the paper money samples were found to be contaminated, as well as just over 88 percent of coins. Money that appeared dirty had greater levels of contamination than money that appeared clean. A control group of uncirculated money (in "mint" condition) showed no contamination, indicating that the contamination occurs during circulation, rather than during manufacture.

Perhaps most disturbing is the strength of the pathogens involved. The Staphylococci found were 100% resistant to treatment with vancomycin, penicillin G, and amoxicillin. The researchers urge, "Hygiene practices during or after handling currency is greatly encouraged to prevent infection."

This study was performed in Cameroon, and the researchers examined local currency (Cameroon Francs). However, studies with similar results have been performed in Ireland (looking at euro currency), India (looking at fungi that pose risks to humans and plants), India again (looking at Staph contamination), the United States (looking at contamination of restaurant and catered food by money-handling among food-prep staff), Turkey (focusing on paper money), and Asia (examining enteric pathogens such as E. coli and Salmonella). Money all over the world has been found to be contaminated with virulent, drug-resistant pathogens that affect people and agricultural plants.

Perhaps most disturbing is how persistent these pathogens are. In one study (performed at the University of Georgia and examining US coins), E. coli placed on the surface of a previously sterile quarter was found to survive for eleven days; Salmonella lived for nine days on the surface of a dime.

Proper handwashing is always important after using a bathroom as well as both before and after handling food. However, the importance of handwashing after handling money has likely been underestimated. It's time to change that.

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