Painstaking work by Wisconsin hospitals in recent years has sharply lowered the occurrence of one of the most deadly types of infections: those from central lines used to deliver fluids, medication and blood to patients. Infections in intensive care units from central lines — tubes placed in a large vein in a patient's neck, chest or arm — were 56% lower last year than a national baseline established in 2008, according to a report by the Wisconsin Division of Public Health. That progress — which included a 21% reduction from 2011 — has stemmed from a series of initiatives since 2009 by the Wisconsin Hospital Association, as well as from projects by individual hospitals.