Thousands of nurses at five Minnesota hospitals launched a strike on Monday, in a dispute over health insurance, workplace safety, and staffing levels. The affected hospitals are all part of Minneapolis-based Allina Health: Abbott Northwestern and the Phillips Eye Institute in Minneapolis, United in St. Paul, Unity in Fridley, and Mercy in Coon Rapids. About 4,800 nurses at those hospitals are represented by the Minnesota Nurses Association, which called the strike.