When you pay with cash, it's likely you're giving the cashier more than money. Bills and coins can spread bacteria – and the currency you use appears to play a major role.
Habip Gedik at the Okmeydani Training and Research Hospital in Istanbul, Turkey, and his colleagues in the Netherlands investigated how well bacteria survived on seven currencies: the euro, US dollar, Canadian dollar, Moroccan dirham, Croatian kuna, Romanian leu and Indian rupee.
The team sterilised banknotes of each currency before coating them with one of three types of bacteria: MRSA, VRE – another antibiotic-resistant bug that can cause hospital infections – or E.coli.
None of the bacteria survived for longer than 3 hours on the kuna. But the leu provided a happy home for all three species for at least 6 hours, and MRSA was detectable on it 24 hours later. No species survived for a day on any of the other currencies.
The team also studied to what extent the euro, leu and US dollar could spread E.coli or Staphylococcus aureus onto people's skin. They made volunteers with clean hands rub contaminated bills for 30 seconds and then tested their fingers for bugs. People who handled euros coated in E.coli were bacteria-free, but those who handled the leu got both types of bacteria on their skin. People who handled US dollars laced with S. Aureus also got the bug on their fingers.
The leu is made of polymer fibres. Polymer banknotes last longer and are harder to counterfeit than traditional cotton-fibre ones, and the Bank of England announced this week that these wipe-clean notes could be introduced from 2016, following the example of countries such as New Zealand and Canada. The notes will be introduced only after a public consultation, although the Bank of England appears convinced of their benefits.
However, the study by Gedik and colleagues shows that plastic notes do appear to provide the best conditions for bacteria to survive and get passed on to others. The researchers think that these notes could help spread bacterial infections.
"I was amazed to see that some currencies act like breeding grounds for bacteria while others seem to be auto-sterilised," says team member Andreas Voss of Radboud University Nijmegen in the Netherlands.
Journal reference: Antimicrobial Resistance & Infection Control, DOI: 10.1186/2047-2994-2-22
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