(1) Any county contiguous to a district maintaining a district public health agency may become a part of the district by agreement between its board of county commissioners and the boards of county commissioners of the counties comprising the district. The county, upon being accepted into the district, shall thereupon become subject to the provisions of this part 5.

(2) Any county in a district maintaining a district public health agency may withdraw from the district by resolution of its board of county commissioners. A county may not withdraw from a district within the two-year period following the establishment of the district or the county becoming a part of the district. A county may only withdraw from a district after one year's written notice given to the agency. In the event of withdrawal of a county from a district, any moneys that had been appropriated by the county before withdrawal to cover its proportionate share of maintaining the district may be returned to the county. A county shall establish a county public health agency or join another district public health agency once the county withdraws from a district.

(3) A municipal corporation that has voluntarily merged its public health agency with a county or district public health agency under the authority of section 25-1-506 may withdraw from the county or district public health agency by resolution of its city council, board of trustees, or other governing body. A municipal corporation may not withdraw from an agency within the two-year period following the municipal corporation becoming a part of the agency. A county may only withdraw from a district ninety days after a written notice is given to the agency.