Rarely washed, frequently shared and constantly touching your mouth, your iPhone could be spreading the flu virus, public health experts say.
But don't be so quick to wipe it down with strong cleaners, which could ruin the touch screen.
With an early, bruising flu season walloping much of the United States, public health experts are repeating the basics for preventing the spread of the virus: Get a flu shot. Stay home when you're feeling lousy. Wash your hands frequently. And thoroughly clean the surfaces you frequently touch.
That final suggestion would be especially sound advice for the millions of Americans with iPhones or other smartphones -- items that, in the last five years, have, for many, become more indispensable than just about any other object we come into contact with.
But that same gadget -- the one that helped you snag last-minute movie tickets and share the adorable video clip of a dancing parakeet -- also happens to harbor many of the qualities conducive to spreading viruses and bacteria.
Doctors note that there have been only a few studies of the spread of the flu through phones, and they maintain that person-to-person contact and dirty hands remain the most common ways of spreading the flu and colds.
They also caution that people not share their phones. And they say that picking up a cellphone after, for instance, shaking hands with someone who is ailing, means that the virus or bacteria will have a short hop into your system via the phone held next to your mouth or face.
So even though your phone looks spotless, it may be teeming with pathogens, according to Professor Chuck Gerba, a microbiology professor at the University of Arizona who studies the spread of germs and viruses in homes, workplaces and public settings.
He's researched cellphones and found that they host disease agents ranging from the flu virus to Norovirus and the dangerous MRSA germ. Out breaks of Norovirus, a highly contagious germ that afflicts cruise ship patrons and school students, has also been plentiful across the country recently.
The real threat from a phone -- as with any other surface -- is when others come into contact with it, thus providing the opportunity for germs to jump between people.
"If you don't share it, it's not much of an issue," Gerba said of cell phones. "But if you do, we recommend wiping it down with a disinfectant."
But here's the rub: phone makers instruct owners not to use strong cleaning solutions, detergents or chemicals, as they could hurt the phone.
On its website, Apple specifically says not to "use window cleaners, household cleaners, aerosol sprays, solvents, alcohol, ammonia, or abrasives to clean" its phones; those substances can damage the screen. Apple says its phones should be cleaned with only a "soft, slightly damp, lint-free cloth."
Samsung, which makes a competing line of touch-screen phones, similarly advises in its owner's manual not to use "harsh chemicals, cleaning solvents, or strong detergents." It recommends wiping the phone with a "soft cloth slightly dampened in a mild-soap-and-water solution."
Neither Apple nor Samsung returned requests for comment.
Other fixes include covering the phone in a plastic cover, which can be cleaned, or expensive UV sanitizers, whose makers claim zap germs.
So just how much of a threat does your phone pose?
Public health experts say they aren't sure -- and finding the exact answer would be difficult. One study published in 2010, concluded that "viruses are readily transferred" between fingers and glass surfaces, like those on smart phones.
The likelihood of contracting an illness from a phone is tied to several factors, including how recently those germs were placed on the phone, said Dr. William Schaffner, chair of the Vanderbilt University medical school's Department of Preventive Medicine.
Your chances of picking up the virus are greatest in the first 15 minutes after it's been placed there, and diminish greatly after a few hours, he said.
Tips on preventing the spread of illness from cell phones:
-- Don't share. You can't contract germs from others -- or spread yours -- if your phone stays in your hands only.
-- Wrap it up. Cover your touch screen with a plastic film, which can be replaced or washed.
-- Let it sit. If someone else has touched your phone, be mindful that it could be a conduit for the flu or colds. If possible, don't use the phone for a few hours. If you must use it, try to use speaker-phone mode.
-- Be especially careful to keep your phone away from children, who are considered the "dominant distributors" of the flu, according to Schaffner, the Vanderbilt expert.