Not later than 180 days after December 19, 2006, the Secretary, in collaboration with State, local, and tribal officials, shall build on State, local, and tribal programs in existence on December 19, 2006, to establish and maintain a Medical Reserve Corps (referred to in this section as the “Corps”) to provide for an adequate supply of volunteers in the case of a Federal, State, local, or tribal public health emergency. The Secretary may appoint a Director to head the Corps and oversee the activities of the Corps chapters that exist at the State, local, Tribal, and territorial levels.