The findings of an exogenous koala retrovirus (KoRV) associated with neoplastic diseases in koalas (Phascolarctos cinereus) brought up the concerns of infection by koala retroviruses in humans, especially koala handlers. As simple retroviruses, koala retroviruses lack the regulatory genes to counter restriction activities by human restriction factors in viral replication. Koala retroviruses belong to gammaretroviruses. Previous studies of susceptibility of murine leukemia virus and a lab contaminant retrovirus, gammaretroviral xenotropic MLV-related virus, to human restriction factors disprove the possibility of gammaretrovirus as a human pathogen. There is no evidence that the koala retrovirus can infect and replicate in human peripheral blood mononuclear cells, which is consistent with the resistant role of human restriction factors against gammaretroviruses.