Viral fitness refers to the inherent ability of a virus to replicate and cause disease.
Sixteen patients were randomly assigned to continue or discontinue antiretroviral therapy with 11 stopping and five continuing. An additional seven patients were enrolled in a non-randomized arm, all of whom discontinued therapy. Viral fitness was also measured at the beginning of the study and 12 weeks after therapy was discontinued. For the five patients who continued therapy, the researchers found that the viral load, the CD4 cell count, and the level of drug resistance remained stable. Viral fitness was markedly reduced and remained low throughout the study.