Fig. 2. Seroprevalence of serum samples or herds in different regions classified by different herd sizes. (A) Sample seroprevalence. (B) Herd seroprevalence. Both sample seroprevalence and herd seroprevalence varied with herd geographical location, and they showed a similar tendency toward west > north > central > south > east. Among the different regions, the seroprevalence of 50‒100-sow herds, as well as the seroprevalence of samples collected from such herds, was highest in the north, while the seroprevalence of larger herds, as well as the seroprevalence of samples collected from such herds, was highest in the west.
