A Seattle hospital says about 650 dialysis patients since 2011 might have been exposed to hepatitis B because of a lapse in screening procedures.

But the Virginia Mason Hospital and Medical Center and King County public health officials said Friday the risk of transmission is low.

Virginia Mason notified health officials in late May that staff had not been consistently screening and isolating patients, which is recommended by the Centers for Disease Control and Prevention.

The hospital urged patients to get tested for hepatitis B.

Dr. Jeff Duchin of Seattle and King County Public Health says an investigation by his agency found the hospital followed other steps, such as disinfecting equipment, to prevent infection.

He says officials found no evidence of increased of risk for acquiring blood-borne pathogen infections in the hospital's dialysis unit. The nonprofit Northwest Kidney Centers is contracted to provide dialysis at the hospital.