High bacteria counts on cellphone doesn't determine rate of infection


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SALT LAKE CITY — Tamra Rossiter is a mom and high school chemistry teacher. She's the first one to admit: "I know for myself I clean my toilet seat more than I clean my phone."

Her two daughters — one in high school, the other in middle school — said they don't clean their phones.

In fact, when KSL Investigators went searching for smartphone owners for an experiment about germs, it became clear many of us aren't in the habit of wiping down our devices.

In all, KSL collected samples from eight cellphones.

Nelson Laboratories in Salt Lake City conducted tests on the samples. Initial results showed bacteria counts between 97 CFU (colony forming units) and 328 CFU. The lab said one of the testing kits had so much bacteria, technicians couldn't count all of them.

Those results did not concern Angela Dunn, M.D, with the Centers for Disease Control. She is assigned to the Utah Department of Health and reviewed the test results.

"Like all other objects, they're going to have bacteria on them. Especially objects that we touch with our hands a lot. And we wash our hands, but we don't necessarily wash our cellphones," Dunn said.


Like all other objects they're going to have bacteria on them. Especially objects that we touch with our hands a lot, and we wash our hands, but we don't necessarily wash our cellphones.

–Angela Dunn, M.D, with the Centers for Disease Control


Germ count alone doesn't offer insight into if the type of bacteria on a cellphone will make a human sick.

Curious if the lab would find troublesome bacteria, such as E. coli, KSL Investigators asked the lab to identify the most prevalent germs on the four dirtiest test results.

The second round of testing revealed the bacteria was the kind typically found on human skin and in the environment — not the kind that would make the people using those phones sick. Even the test result that had too many germs to count did not show harmful bacteria.

The CDC recommends not taking your phone into germy places such as bathrooms, washing your hands, not sharing phones (if you do, wiping them off), and cleaning your phone about once a week.

As part of this experiment, KSL Investigators used cleaning wipes available at a local cellphone store. Although some bacteria was still detected, results showed a significant reduction in the total number of germs.

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Debbie Dujanovic

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