S.D. Codified Laws § 34-3-3
There shall be created in each county maintaining a full-time county health department, a county board of health consisting of seven members to be appointed by the county commissioners as follows: One member shall be a member of such board of county commissioners, appointed for one year at the first official meeting of such board in each calendar year; one member shall be a practicing physician and shall hold office for a term of four years; five members are to be selected from the electors of the county to hold office for terms of five years each, except that the initial term shall be staggered in such manner that the term of one board member so chosen shall expire each year. Vacancies occurring on the county board of health shall be filled by appointment by the board of county commissioners for the unexpired term affected.
SDCL 34-3-3