Clostridium difficile, a bacterium that causes severe diarrhea and 30,000 deaths each year in the U.S., has long been thought to infect hospitalized patients or people in other healthcare facilities. But in a study published online on December 11 in Infection Control & Hospital Epidemiology, researchers report that nearly 1 in 10 patients admitted to the hospital are already infected with C. diff, even though they do not have symptoms.

The researchers, led by Sarah Baron, M.D., M.S., tested 220 incoming hospital patients with no symptoms of C. diff and found that 21 were infected. Within six months, 38% of those carriers progressed to symptomatic C. diff—most within the first two weeks of hospitalization; by contrast, only 2% of initially non-infected patients ended up with symptomatic C. diff.

The U.S. Centers for Disease Control and Prevention considers prospectively identifying C. diff carriers a supplemental intervention but doesn’t recommend it as a prevention strategy. This study suggests that prospectively identifying and treating carriers could help prevent C. diff-related illnesses and deaths. Dr. Baron is assistant professor of medicine at Einstein and director of Inpatient Quality Improvement in the department of medicine at Montefiore.