50th anniversary of ATM

We live in a dirty world. Wherever we go, we are among microbes. Bacteria, fungi and viruses live on our phones, bus seats, door handles and park benches. We pass these tiny organisms to each other when we share a handshake or a seat on the plane. Now, researchers are finding we also share our microbes through our money. From tip jars to vending machines to the meter maid – each dollar, passed person to person, samples a bit of the environment it comes from, and passes those bits to the next person, the next place it goes.

Disease transmission linked to money is rare, and no major disease outbreaks have started from our ATMs. Although it doesn’t seem common for diseases to transmit through money, there are ways we could make our money cleaner.

Researchers are working on ways to clean money between transactions. Putting older bills through a machine that exposes them to carbon dioxide at a specific temperature and pressure can strip dollar bills of oils and dirt left behind by human fingers, while the heat kills microbes that would otherwise linger.

U.S. money is still made from a blend of cotton and linen, which has been shown to have higher bacterial growth than plastic polymers. Several countries are transitioning from money made of natural fibers to plastic, which may be less friendly to bacteria. Canada has had plastic money since 2013, and the U.K. transitioned to a plastic-based bank note last year.

Even if our money is not directly responsible for spreading disease, we can still use the dollar’s travel history to track how we spread disease in other ways. The website WheresGeorge.com, created in 1998, lets users track dollar bills by recording their serial numbers. In the almost 20 years since the site’s creation, WheresGeorge has tracked the geographic locations of bills totaling over a billion dollars.

Now, physicists at the Max Planck Institute and University of California, Santa Barbara are using data from the WheresGeorge site to track epidemics. Information on human movement and contact rates from WheresGeorge was even used to predict the spread of the 2009 swine flu.

Although we don’t know the extent to which money allows diseases to spread, mom’s advice is probably best when handling cash: Wash your hands and don’t stick it in your mouth.