This question was addressed by Abrahams, Joseph et al., who used samples from nine HIV-1 clade C-infected South African women to compare pre-ART HIV-1 RNA (longitudinally sampled from the plasma during 2.7–6.9 years of untreated infection) to replication competent HIV-1 in resting CD4+ T cells obtained post-ART (after 4.7–6.1 years of ART) (2). Here, CD4 is linked to infection.