Cercocebus atys: A species of Old World monkeys from the genera CERCOCEBUS that is important in AIDS research. They may be naturally or experimentally infected with the SIMIAN IMMUNODEFICIENCY VIRUS. They inhabit African forests from Sierra Leone to the Congo Republic.Cercocebus: A genus of the subfamily CERCOPITHECINAE inhabiting the African forests. They are also known as mangabeys.Cercopithecidae: The family of Old World monkeys and baboons consisting of two subfamilies: CERCOPITHECINAE and COLOBINAE. They are found in Africa and part of Asia.Monkey Diseases: Diseases of Old World and New World monkeys. This term includes diseases of baboons but not of chimpanzees or gorillas (= APE DISEASES).Simian immunodeficiency virus: Species of the genus LENTIVIRUS, subgenus primate immunodeficiency viruses (IMMUNODEFICIENCY VIRUSES, PRIMATE), that induces acquired immunodeficiency syndrome in monkeys and apes (SAIDS). The genetic organization of SIV is virtually identical to HIV.Primate T-lymphotropic virus 3: A species of DELTARETROVIRUS that includes the strains SIMIAN T-LYMPHOTROPIC VIRUS 3 and HUMAN T-LYMPHOTROPIC VIRUS 3.Ape Diseases: Diseases of chimpanzees, gorillas, and orangutans.Simian T-lymphotropic virus 1: A strain of PRIMATE T-LYMPHOTROPIC VIRUS 2, closely related to the human HTLV-1 virus. The clinical, hematological, and histopathological characteristics of the disease in STLV-infected monkeys are very similar to those of human adult T-cell leukemia. Subgroups include the African green monkey subtype (STLV-I-AGM), for which the nucleotide sequence is 95% homologous with that of HUMAN T-LYMPHOTROPIC VIRUS 1, and the Asian rhesus macaque subtype (STLV-I-MM), for which the nucleotide sequence is 90% homologous with that of HUMAN T-LYMPHOTROPIC VIRUS 1.Deltaretrovirus Infections: Infections caused by the HTLV or BLV deltaretroviruses. They include human T-cell leukemia-lymphoma (LEUKEMIA-LYMPHOMA, T-CELL, ACUTE, HTLV-I-ASSOCIATED).Cameroon: A republic in central Africa lying east of CHAD and the CENTRAL AFRICAN REPUBLIC and west of NIGERIA. The capital is Yaounde.Phylogeny: The relationships of groups of organisms as reflected by their genetic makeup.