From the Document: "Homeland Security Presidential Directive 7 (HSPD-7) identified 17 sectors of the U.S. economy and designated Federal Government Sector-Specific Agencies (SSAs) for each of the sectors. Each sector is responsible for developing and submitting Sector-Specific Plans (SSPs) and sector-level performance feedback to the Department of Homeland Security (DHS) to enable national cross-sector critical infrastructure and key resources (CI/KR) protection program development and gap assessments. SSAs are responsible for collaborating with public and private sector security partners and encouraging the development of appropriate information-sharing and analysis mechanisms within the sector. The Department of Health and Human Services (HHS) is the SSA for the Public Health and Healthcare Sector."
U.S. Department of Homeland Security: http://www.dhs.gov/