There has been much uncertainty in the relationship between PCV2 and PMWS but Bolin et al demonstrated that Koch's postulates could be fulfilled by inoculating cesarean-derived, colostrum-deprived (CDCD) pigs with PCV2 and producing clinical signs of PMWS. Similar work has been performed using an infectious genomic clone of PCV2 in specific pathogen free (SPF) pigs to produce the gross and microscopic lymphoid lesions of PMWS. Although PCV2 has been shown to induce PMWS lesions in CDCD and SPF pigs, the presence of additional factors are required.