S.D. Codified Laws § 34-3-10

A full-time district health department shall be construed to be a department organized to serve contiguous territory in two or more adjacent counties, and which shall be under the immediate direction of a health officer and employing trained public health personnel who shall devote their entire working time to the prevention of disease and the promotion of public health, provided that physicians may be employed on a part-time basis to act as assistant health officers.