Is viral shedding a surrogate marker for transmission of genital herpes? A discussion document.

While the concept linking herpes simplex virus (HSV) shedding to transmission is plausible, few data support shedding as a surrogate marker. If shedding is to be used as a surrogate marker in future clinical studies, it must be clear how far shedding must be reduced, and what the shape of the transmission:viral load curve (or transmission:detection frequency curve) is before transmission is reduced. It remains unclear whether peak virus load, frequency of detection of virus, or the area under curve of the time:virus load plot is the critical parameter in the transmission of HSV. This paper reports on an international meeting of experts and a debate at the International Herpes Management Forum (IHMF) Annual Meeting (2004), convened to examine whether a surrogate marker for HSV transmission is necessary, and whether there is any evidence, either in studies involving HSV or other viral infections, to suggest that viral shedding could be used as such a surrogate.