Testing cell phones for bacteria and viruses could tell doctors who has been exposed to potentially deadly microorganisms.

Our bodies play host to around 100 trillion microbes that together weigh more than 2 pounds. They are present on our skin, in our guts, in the crooks of our elbows, and just about everywhere else.

These bacteria, viruses, and fungi, collectively called the microbiome, help us digest our food and fight off infections. And emerging research shows that modifying our personal mix of microbes may even help treat chronic conditions like diabetes and Crohn’s disease.

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To get an idea of just how many microbes we carry—and which ones—researchers are testing our most intimate possessions: our cell phones.

In a small study, University of Oregon scientists tested the index fingers and thumbs of 17 subjects, along with the touchscreens of their smartphones. As you might expect, they found an 82 percent overlap between the most common types of bacteria found on participants’ fingers and on their phones. Women tended to have more bacteria in common with their phones than men.

Of the more than 7,000 different types of bacteria the researchers identified, the most common were in the Streptococcus, Staphylococcus, and Corynebacterium families. These bacteria are typically found in the human mouth and on the skin.

Though some strains of Streptococcus, Staphylococcus, and Corynebacterium can make people sick, especially if they have a weakened immune system, research suggests that these bacteria help protect ­­­­the skin, in part by competing with harmful strains for space and resources.

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The new study was published today in the open-access journal PeerJ.

“This project was a proof-of-concept to see if our favorite and most closely held possessions microbially resemble us,” said lead author James Meadow, a postdoctoral researcher at the University of Oregon, in a press release. “We are ultimately interested in the possibility of using personal effects as a non-invasive way to monitor our health and our contact with the surrounding environment.”

Indeed, Meadow’s team speculates that swabbing smartphones for bacteria could make large-scale surveys of the human microbiome easier.

More importantly, testing cell phones in hospitals for harmful bacteria like Methicillin-resistant Staphylococcus aureus (MRSA) and Clostridium difficile (C. diff) could give doctors advance warning about which patients and healthcare workers may have been exposed to these pathogens. In some hospitals, as many as one in 25 patients will contract a healthcare-associated infection like MRSA or C. diff during their stay, according to the Centers for Disease Control and Prevention (CDC).

Testing cell phones for harmful bacteria could even be useful in cases of potentially widespread exposure to a pathogen, as happened two weeks ago when more than 80 employees at CDC labs were accidentally exposed to a live strain of the deadly anthrax virus. If the virus were found on a lab worker’s cell phone, it would indicate that the worker may have touched or inhaled the virus in the recent past.

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