Which items have the most germs?
CBS News correspondent Kelly Wallace reported that scientists now say it's the things we use most that harbor the most germs, and the more germs, the more likely viruses are present.
Just where are these germ factories?
Dr. Charles Gerba -- also known as "Dr. Germ" -- has been tracking the levels of disease-causing bacteria for 10 years. He uses a germ-meter, which gives a relative idea of how many bacteria are living on a surface.
Gerba, of the University of Arizona, found after conducting more than 7,000 studies that the most germs per square inch are on the things we touch the most, such as cell phones. In fact, says Gerba, they're No. 1 on his list.
Wallace says more than 203 million Americans currently own a cell phone. She cited a recent study, published a study in the Annals of Clinical Microbiology and Antimicrobials, that showed 94.5 percent of cell phones used by health care workers had evidence of bacterial contamination.