Figure 1.

Box plot of the survival of bacteria on banknotes over time. Open boxes and closed dots: cotton-linen notes (Chinese yuan); Closed boxes and open dots: polymer (Australia dollar). Data shows recoverable bacteria after a single extraction. The bacterial inoculum (hand microbiome) in this experiment was facilitated by soaking the notes in nutrient broth in which volunteers washed their hands. The bacterial loading of the broth at the time of removing the notes from the broth was approximately 1 × 10¹¹ CFU (colony forming units)/mL. The boxes represent the interquartile range (central 50%) of the data regarding the number of bacteria on banknotes analysed. The dots represent the average number of recoverable bacteria, whereas the whiskers (viz. error bars) represent either the upper or lower 25% of banknotes analysed (n = 30).