GREM2 and infection: When compared with previous studies that systematically analyzed the coinfection association of PPVs and PCVAD from archived tissue samples confirmed as positive for PCVAD or PRDC [23, 25, 29] and from serum samples with subclinical infection of PCV2 [24], PPV1 and PPV6 were consistently correlated with PCVAD, as identified in the current study (Table 6).