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I don't think Cary really answered the question here. The letter writer did not ask if s/he should ever tell their sexual partners that they had herpes, the LW asked whether it was appropriate to include this information upfront in a personal ad, or if it was okay to wait until getting to know the person better. For this question, I would say no, one is not obligated to include the information in a personal ad, and while it goes without saying that the LW must inform all sexual partners, I don't think it's necessary to disclose his/her condition until s/he decides that they've found a person with whom they would actually like to have sex. Placing the information in a personal ad is bold, and might work for some people, but it also could cause people to define the LW as merely a "person with herpes", possibly overlooking their other desirable qualities due to the shadow cast by the word STD. It's perfectly fine to get to know a person first and then inform them in an appropriate context (e.g., after things have warmed up a bit between the two, saying something like "Before we go any further, I need to tell you something..."). This way the LW has already established his/herself as attractive to a partner without letting the virus define them. As the LW admitted, the conversation is absolutely necessary...but no, it doesn't need to be the first thing they tell someone. I don't believe this is dishonest. It's awkward enough to meet a person to begin with, and people with herpes are certainly not "lepers". Wait until you find someone who you are attracted to and who is attracted to you back. If they are worth your while, they will take the conversation in stride.
The only possible danger I see is the LW (or anyone with an STD, for that matter) could keep putting off and putting off the conversation until things got to a dangerous place. That, however, is a moral question and not a practical one. As long as the LW is prepared to have the conversation, it's not terribly important _when_ it happens, as long as it occurs before sex (or any similarly perilous point).