A case of venereal disease shall be regarded as infectious until a physician licensed to practice medicine has examined the case and reported to the local board that the case is not infectious, but if in the opinion of the local board of the jurisdiction the protection of the public health requires it, the board may review the case and cause a medical examination of any such case to be made by a physician designated by the board, and the opinion of such physician as to the infectiousness or noninfectiousness of the case shall be final.