If you read them carefully, the two quotes don't really conflict with one another. The first quote refers primarily to when transmission is highest risk (early in relationships). The second part of it indicates the uncertainty ("many [most?]") of the data.
The second quote could be restated as "most (many?)".
The greatest risk of transmission tends to be early in relationships, for reasons that aren't entirely clear--probably some mix of how recently herpes was acquired by the infected person, frequency of sex, level of passion (which could affect judgment during minor symptoms), duration and vigor of intercourse, and similar factors. The risk declines as a relationship matures, but it is likely that more than half of all discordant couples end up sharing the infection.
I hope that helps. Best wishes-- HHH, MD
Dr.HHH, Thanks again for your continued efforts in this forum and for your clarification.
I am going to summarize your reply this way, that more than half of discordant couples will share the infection and that transmission would most likely occur within the first 2 years of a relationship. The longer the relationship, after 2 years, that the non-infected partner goes without being infected, the less likely, but not absolutely, they will become infected, in your opinion.
I appreciate your attention and interest.
Good summary, there probably isn't a sudden decline in transmission risk at 2 year. The risk probably declines in a gradual fashion, ie higher risk in the first 6 mo than at a year, lower still at 2 yr, and likely lower still after that. The available data don't permit more precision than this, and I suspect the transmission potential continues to decline for several years. But it never hits zero.
I have HSV1 and 2. I'd read that the transmission rate from female to male is around 4%/year, and male to female around 8%/year. That's pretty much what I've been telling my partners, and we've all found that statistic quite reassuring. However, if the transmission rate can be as high as your post suggests, that's another story. Granted, I'm only having occasional sex with these partners, but still. I want to be sure I'm as accurate as possible in detailing the risks.
I'll just add that I've never had an obvious outbreak (aside from a painful "yeast infection" a few years ago that I now think was an outbreak). I also always use condoms for intercourse, but give and receive unprotected oral. Am I putting my partners at significant risk? Should I consider suppressive therapy?