| human t-lymphotropic virus 1 | no rank | viruses and viroids | viruses | no rank | 11908 |
| primate t-lymphotropic virus 1 | species | viruses and viroids | viruses | species | 194440 |
| simian endogenous retrovirus | | | | no rank | 1048243 |
| simian foamy virus | species | viruses and viroids | viruses | species | 11642 |
| simian immunodeficiency virus | species | viruses and viroids | viruses | species | 11723 |