CD4 count patterns over time after seroconversion. Scatterplot of CD4 T-cell count values after seroconversion (grey points), together with the fitted least squares curve (i.e. average CD4 T-cell count values; thin grey line) and the fitted curve from the random effects model (i.e. average CD4 T-cell count patterns; thick black line, with 95% confidence intervals). Average patterns for the groups defined by progression times (in years) are shown as well (dashed grey lines).