Moving? Your Germ Universe Will Follow

It doesn't matter how much we scrub—our bodies are home to trillions of bacteria. And a new study finds that they travel with us: Even when we move to a new location, they colonize those surfaces within about a day, reports WebMD. But the vast majority that comprise what's called our microbiome seem to do helpful things, like keep our immune and digestive systems healthy. And because one family's microbiome is unique from another's, the researchers say that comparing them among the seven families they tracked (including three kids, three dogs, and a cat) was a reliable way to tell them apart, much like fingerprints.

"The speed at which that colonization happens was quite remarkable," the head researcher tells AP. His team found that a place's old germs largely go dormant or die when new people arrive and their own bacteria take over, which "changed my perspective almost on hotel rooms," he says. Within homes, similar bacteria was most often found on people's hands, while variation peaked when found in people's noses. Not surprisingly, indoor-outdoor cats and dogs bring plant and soil bacteria into the environment. One open question: Where do the bugs we bring into our homes come from? (Scientists behind the Human Microbiome Project say we should treat our bodies the way environmentalists treat wildlife preserves.)