What is what hospital is oak street health affiliated with?

Oak Street Health is not affiliated with any specific hospital in the traditional sense of a parent-subsidiary relationship or a formal merger. They are a separate, independent company. However, they work with many hospitals and health systems across the geographic areas they serve. Their relationships are focused on care coordination and referrals, not ownership. A patient's care might transition between an Oak Street Health center and a local hospital as needed, but Oak Street Health isn't "part of" any particular hospital system.