Viral infection using the PERV-A and PERV-A/C Env-pseudotyped viruses was confirmed in MDTF-chSLC52A2, MDTF-huSLC52A2, MDTF-chSLC52A1, and MDTF-huSLC52A1 cells (Fig. 1A), thereby indicating that chimpanzee and human SLC52A2 and SLC52A1 expression confers susceptibility to infection with pseudo-typed PERV. The gene discussed is SLC52A1; the disease is viral infectious disease.