Our results are consistent with increased virulence of HIV-1 over the course of the epidemic. Extrapolating over the 30 years since the first description of AIDS, this represents a CD4(+) T cells loss of approximately 148 cells/μl and a gain of 0.39 log(10) copies/ml of viral RNA measured during early infection. These effect sizes would predict increasing rates of disease progression, and need for ART as well as increasing transmission risk.
We searched PubMed for studies of trends in HIV-1 prognostic markers of disease progression and supplemented findings with publications referenced in epidemiological or virulence studies. We identified 12 studies of trends in baseline CD4(+) T-cell counts (21, 052 total individuals), and eight studies of trends in set point viral loads (10 ,785 total individuals), spanning the years 1984-2010. Using random-effects meta-analysis, we estimated summary effect sizes for trends in HIV-1 plasma viral loads and CD4(+) T-cell counts.
The potential for changing HIV-1 virulence has significant implications for the AIDS epidemic, including changing HIV transmission rates, rapidity of disease progression, and timing of ART. Published data to date have provided conflicting results.
We conducted a meta-analysis of changes in baseline CD4(+) T-cell counts and set point plasma viral RNA load over time in order to establish whether summary trends are consistent with changing HIV-1 virulence.
Baseline CD4(+) T-cell counts showed a summary trend of decreasing cell counts [effect = -4.93 cells/μl per year, 95% confidence interval (CI) -6.53 to -3.3]. Set point viral loads showed a summary trend of increasing plasma viral RNA loads (effect = 0.013 log(10) copies/ml per year, 95% CI -0.001 to 0.03). The trend rates decelerated in recent years for both prognostic markers.