CD4 and immunodeficiency disease: Studies carried out in China, where variant CRF01_AE is the most predominant clade, revealed that this variant is associated with fast progression to AIDS (with a shorter median time from the estimated date of seroconversion to AIDS) and advanced immunodeficiency (shorter median time from estimated date of seroconversion to CD4 cell count <100 cells/μl) as compared to non-CRF01_AE viral clades [22, 23].