Cumulative positivity rate for infections with HPV types 16, 18, 31, and 45 according to tertiles of cumulative viral load for these 4 types. Unit of analysis is an individual infection episode, which makes observations not independent as a subject may contribute multiple episodes. Dotted line: upper tertile; dashed line: middle; solid line: lower tertile viral load.
Ramanakumar et al. BMC Infectious Diseases 2010 10:326 doi:10.1186/1471-2334-10-326