Among the types of germs that Dr. Philip Tierno has looked at, include those found on paper currency. A study by Dr. Peter Ender of the Wright Patterson Medical Center in Dayton, Ohio found that dollar bills might be capable of spreading disease.
To gather a sample to study, they swapped new for old bills at a concession stand and grocery store. Among the 68 bills they gathered, just four were found to be free of bacterial contaminants. Of the remaining dollars, 59 had microbes such as Streptococcus that can cause infections in hospitalized people or those with compromised immune systems. The remaining five bills had bacteria including Staphylococcus aureus and Klebsiella pneumoniae that can cause infection in healthy people.
"One-dollar bills are widely used and each is exchanged many times...If some bills are contaminated with bacteria, there is potential to spread these organisms from person to person," Ender told a meeting of microbiologists. But he cautioned that the small sampling of only 68 bills may not be representative and that his study didn't actually look at whether transmission of germs occurred from handling the bills.