A HIO, by definition, cannot participate as part of an OHCA because the HIPAA Privacy Rule defines OHCA as an arrangement involving only health care providers or health plans, neither of which a HIO qualifies as. However, a HIO may be a business associate of an OHCA if the HIO performs functions or activities on behalf of the OHCA. See 45 C.F.R. § 160.103 (definitions of “organized health care arrangement” and “business associate”). For example, a hospital and the health care providers with staff privileges at the hospital are an OHCA for purposes of the Privacy Rule. To the extent such an arrangement uses a HIO for electronic health information exchange, the HIO would be a business associate of the OHCA.