(See the editorial commentary by Quinn, on pages 495–8.)

Background.  Herpes simplex virus type 2 (HSV-2) reactivations in the genital tract are responsible for mucocutaneous lesions and transmission and manifest as discrete shedding episodes.

Methods.  We analyzed duration, peak copy number, and expansion and decay rates of 1020 shedding episodes in 531 immunocompetent HSV-2–seropositive persons from whom daily swabs of genital secretions were collected.

Results.  Viral quantity varied by as much as a multiple of 10 million in a single person over time. Peak episode copy number was distributed approximately evenly from 10³ through 10⁸ HSV DNA copies/mL. Median rate of increase was 10^7.6 HSV DNA copies/day during the first 12 hours of an episode and 10⁵ copies/d from episode initiation to peak. These values depended only moderately on episode duration. Median decay rate was –10^6.2 HSV DNA copies/d during the final 12 hours of an episode and –10^3.6 copies/d from peak to termination. Episodes lasted a median of 3 days (interquartile range, 1–8 days). Prolonged (>5 days) episodes were associated with nonmonotonic decay.

Conclusions.  HSV-2 shedding episodes are notable for rapid expansion and decay and extreme heterogeneity of duration and viral production. The net effect of these dynamic episodes is frequent shedding at high copy numbers.