More hospital patients have Clostridium difficile than previously thought, according to a new study by the Association for Professionals in Infection Control and Epidemiology.

Thirteen out of every 1,000 inpatients were either infected or colonized with the germ, the one-day study found. A total of 648 hospitals participated and 1,443 patients with the bacteria were identified. C. difficile, which is often associated with previous antibiotic use, is a major problem in long-term care facilities. It can cause diarrhea and spread quickly through a facility. The study took place on one day between May and August.

APIC estimates that C. difficile affects more than 7,000 patients each day in hospitals. Costs to care for the infection range from $17.6 million to $51.5 million, APIC said in its study. The rate is 6.5 to 20 times higher than previously thought, according to APIC.