Taken together the results of growth rate analyses, the presence of co-infecting viruses HetPV13-an1 and HetPV15-pa1 is causing a stable and significant negative effect on their host, whereas the presence of HetPV11 strains has variable phenotypic effects on their hosts when present in combination with HetPV13-an1, and no effects as single infections. The gene discussed is PAGR1; the disease is infection.