The hospital, as the saying goes, is no safe place for a sick person. A new study suggests one reason why: One in three seniors who spend time in a hospital leave with at least one type of antibiotic-resistant “superbug” bacteria on their hands.

The findings, published in a JAMA Internal Medicine research letter, are based on a University of Michigan study that tracked 357 seniors admitted to several regional medical facilities for care or surgery, Fox News reports.

Of these patients, 24 percent had at least one or multidrug-resistant microbe on their hands when they checked in. The patients were again tested after spending two weeks at the facility, and then monthly for up to six months or until discharge. Follow-up testing suggested that not only did the superbugs persist, but that the number of patients with superbugs on their hands increased to 34 percent.

“We’ve been educating health care workers for decades about hand hygiene, and these numbers show it’s time to include patients in their own hand hygiene performance and education,” lead study author Dr. Lona Mody, associate chief for clinical and translational research at the University of Michigan Geriatrics Center, said in a news release.

In the news release, Mody noted seniors often stay in facilities that offer group activities and social events, which could lead to the superbugs further spreading. Frequent antibiotic use in these centers may also cause certain strains of several infectious bacteria to evolve and become resistant to treatment.

“Patient handwashing is not a routine practice in hospitals,” Mody said. “We need to build on the overarching principles we’ve already developed with adult learning theories and bring them to patients.”