This week I was in Seattle at a non-infection prevention conference with 4000 people. I was able to catch up over coffee with an old friend and eat some wonderful local food, but without a doubt observed some questionable infection control practices (e.g. poor and/or non-existent hand hygiene practices made more difficult by the minimal soap that was dispensed….) so I avoided the using any ice and was careful with my choices in food in the buffet line at breakfast and lunch. Of course, after reading a new study on the trip to Seattle by Andreas Voss from the Netherlands I also chose not to use any cash and stuck to the use of my MasterCard or Apple Pay.
Did you know that by time your money is taken out of circulation it will have touched hundreds and most likely even thousands of people’s hands? Think about your use of money: we readily withdraw it from the bank, hand it over when purchasing and readily take back the change from strangers. Just think about how many dirty hands the bill could have touched over the course of its life! In Voss’ study, they looked at currency from the US, Europe, Canada, India, Romania, Morocco and Croatia and found that our currency can in fact harbor and spread some nasty bugs. The upside is that currency used by the USA and EU that is made with a mixture of fibers like cotton and stabilizers like gelatin seem to minimize the ability to allow bacteria to proliferate and/or allow those bugs to transfer to the hands of the next users. The downside is that currency that is more plastic-based seems to have more of an affinity for growing and sharing anything that may be on it. The study concluded that the Romanian leu, is quite literally the dirtiest money known to humankind!
Voss’ team used MRSA, VRE and ESBL E. coli as their “bugs du jour”. The bills were sterilized with UV light, squirted with bacteria, and then allowed to dry before being tested at 3, 6, and 24 hours post inoculation. They also conducted trials with less-dangerous bacteria where test subjects rubbed the bills between their hands for 30 seconds, to see if anything rubbed off. The good news is that while many bills retained their bacteria after 3 hours, by 24 hours most showed no more bacteria. The big exception was the leu, a polymer-based bill continued to exhibit growth of all bacteria after six hours, and some remaining MRSA even after a day. When it came to the transfer test, the Euro did not transfer any of the bacteria tested and the US bill transferred single colonies of Staph. The Leu on the other hand transferred multiple segments of Staph and E. coli.
All in all, the findings - while interesting and a bit gross - are not really a threat to public health. However, after handling money you definitely want to wash your hands, so be sure to have a tube of hand sanitizer handy!