cells) were assessed for their susceptibility to CERV1 infection and were found to be resistant to CERV1, PERV-A, and PERV-A/C infections (Fig. 2C), thereby indicating that CERV1 interferes with the infection of both PERV-A and PERV-A/C via at least Env-mediated interference. The gene discussed is ERVW-1; the disease is infection.