Both hospital patients and their visitors may want to consider leaving their cell phone at home. A recent Turkish study found that their cell phones were covered in pathogens — disease causing bacteria.

Cell phones have not yet been positively linked to hospital infections, but this is the second study suggesting that they may serve as a reservoir of dangerous bacteria capable of causing hospital-acquired infections in patients.

Swabs taken from the phones and from workers' hands revealed similar numbers and types of bacteria, including MRSA.

There are an estimated 1.7 million hospital-acquired infections in the U.S. every year and they're associated with around 100,000 deaths.

The focus on cell phones as a possible infection source was inspired by another study back in 2009. That study found that 95% of the cell phones of doctors and nurses in operating rooms and intensive care units were contaminated with bacteria. Swabs taken from the phones and from workers' hands revealed similar numbers and types of bacteria, including MRSA. Staphylococcus aureus was found on about one-quarter of the phones and 52% were methicillin resistant.

The new study found that visitor and patient phones were considerably more contaminated than those of hospital employees. Roughly 40% of the non-employee phones tested contained disease-causing bacteria, compared to 20% of the employee phones. And the phones of patients and visitors were much more likely to contain multi-drug resistant pathogens than the hospital workers' phones were.

This 2011 study looked at 200 phones, 133 belonging to patients, their companions and visitors and 67 medical employees' phones. Swab samples were collected from earphone, keypad and speaker, and these samples were then grown on appropriate culture medium to determine the types of bacteria present on the phones.

While no one is quite sure yet just how big a threat cell phones pose to hospital infection control, the two studies have raised concerns. Whether they will lead to the creation of cell phone-free zones in hospitals or specific sterilization procedures for the cell phones remains to be seen.

Many cell phone owners report cleaning their phone with a cloth or swab lightly moistened with alcohol. This also helps sterilize the phone. Because alcohol can damage some types of phone screens and the phone's internal parts, people doing this for the first time run the risk of ruining their phone. If this happens, they can at least take comfort in knowing that a newly-bought phone should be a lot cleaner and freer of bacteria than the old one was.

The 2011 study was published in the June issue of American Journal of Infection Control. The 2009 study was published in the March 6, 2009 issue of Annals of Clinical Microbiology and Antimicrobials and is freely available.