Never keep your toothbrush on your bathroom sink. According to a study by the University of Manchester in England, an average toothbrush can contain 10 million bacteria or more, including E. coli and Staph. According to scientists bacteria and viruses falling from toilet spray remain airborne long enough to settle on surfaces throughout the bathroom. An English study found that diarrhea-causing bacteria from a lidless flush flew as high as 10 inches above the toilet. And if the brush falls on the toilet floor it is coming into contact with toilet spray particulate that has settled there.