Statistical analysis on the differences between transmission rates to virus-free and pre-infected recipients indicated that six out of the 12 viral interactions were affected significantly by pre-infected viruses including transmission of HetPV13-an1 to pre-infected host with HetPV11-au1 (P = 0.005), HetPV15-pa1 to the hosts pre-infected with HetPV13-an1 (P < 0.001) or HetPV11-au1 (P < 0.001), HetPV11-au1 to the hosts with pre-existing viruses HetPV15-pa1 (P = 0.041) or HetPV11-pa1 (P < 0.001), and HetPV11-pa1 to the host containing HetPV11-au1 infection (P < 0.001). This evidence concerns the gene PAGR1 and infection.