Figure 5.

For each simian/human immunodeficiency virus (SHIV)–positive animal (9 of 9 in the sexually transmitted infection [STI]–positive group and 4 of 7 in the control group), the sampling time point at which plasma SHIV_SF162p3 RNA was first detected was plotted by the respective day of the menstrual cycle. Plasma progesterone levels were monitored throughout the study course, and day 1 was defined as the time point immediately following the steep progesterone decline (as described in Figure 2). Plasma SHIV_SF162p3 RNA in STI-positive animals (grey bars) was detected later in the menstrual cycle, compared with controls (black bars; P = .01, by the Wilcoxon test).