Infection with human retroviruses is responsible for global epidemics and significant morbidity and mortality worldwide. The current global estimates of infected people are 38 million for HIV-1, 1-2 million for HIV-2, 10 million for human T-cell leukemia virus type 1 (HTLV-1), and 3 million for HTLV-2. Although HTLV-1 and HTLV-2 do not cause AIDS, infection with HTLV-1 has been associated with the development of subacute myelopathy and T-cell lymphomas in nearly 10% of carriers lifelong (Pasquier et al., Front Microbiol 2018; 9: 278). In contrast, HTLV-2 infection is generally asymptomatic although occasionally, it may cause neurological syndromes resembling HTLV-1-associated myelopathy (HAM)/tropical spastic paraparesis (TSP)