May 23, 2001 -- If you believe in putting your money where your mouth is, you may want to think again -- those greenbacks could be crawling with disease-causing bacteria, say researchers at a meeting of the American Society of Microbiology in Orlando, Fla.
U.S. Air Force doctors in Ohio collected 68 one-dollar bills at a grocery store and a concession stand at a high school sporting event in Dayton, and examined them for bacterial contamination. They found that 59 bills were infested with the types of bacteria that can cause infection in people with weakened immune systems. In addition, five of the bills had bacteria that can cause serious forms of pneumonia even in healthy people.
The message? "We emphasize good hand-washing techniques, not only for physicians in the hospital but also for the general public when they're out and about," says co-author Ted Pope, MD, a resident physician with U.S. Air Force Medical Services Flight, 74th Medical Group, at Wright-Patterson Medical Center.
In their study, Pope and colleagues asked patrons at the two test sites if they would exchange one of their bills for a newly printed one. They then subjected the bills they collected to standard laboratory tests for the presence of bacteria. The tests could detect the presence of a specific bacterium, but not whether it was present in large, small, or trace quantities.
The researcher found that five bills were contaminated with the organisms Staphylococcus aureus and Klebsiella pneumoniae, both of which can cause serious cases of pneumonia.
In addition, 59 more bills were contaminated with other strains of Staphylococcus, as well as Streptococcus, Enterobacter, Pseudomonas, and other types of bacteria that can cause illness in people who are hospitalized or those with immune systems weakened by disease or medical treatments such as chemotherapy. Only four of the bills appeared to be germ free, they noted.
Pope tells WebMD that the researchers did not address the question of whether bacteria could actually be spread as the contaminated money changes hands: "That would require more intense study and genetic testing to make sure that a certain bacterium has actually been spread from one person to the next," he says.
But the study does raise troubling questions about food handlers, such as cafeteria and concession workers, who regularly juggle both food and money hundreds of times a day.
And if the study results have you tempted to trade in your paper portraits of George Washington for the new gold-colored dollar coin, forget it, says a University of Georgia researcher who previously studied whether pocket change could harbor dangerous food-borne bacteria such as E. coli and Salmonella.
"We took currency, cleaned it, and then applied some bacteria that are known to be food-borne pathogens to the surface to see if they died off," says Michael P. Doyle, PhD, professor of food microbiology at the University of Georgia, in Athens. "I was always under the belief that copper and some of the metals that are present in coins would have antimicrobial activity and that these bacteria would die off quickly, and that people who are working as cashiers don't have to worry about contaminating food after they handled coins. We were a bit surprised when we found that if you did have salmonella or E coli... on the surface, the organisms could survive for several days."
Doyle was not involved in the USAF paper currency study.
According to the Federal Reserve Bank of Atlanta, the average life of a $1 bill is about 18 months. During that time, it may pass through hundreds or thousands of hands, giving any bugs that happen to be on it plenty of time to hitch a ride.
Asked what those of us who handle money regularly -- most of the human race, that is -- should do to protect ourselves, Doyle also recommends regular hand washing.
"Those people who are handling the cash drawer shouldn't be handling food and money intermittently -- they ought to wash their hands in between," he tells WebMD.