Herpes in Gay couples

[alwaysamommy.livejournal.com]

This doesn't actually apply to me but I was curious. Last night, I was watching the commercial for Valtrex. At the bottom of the screen, a disclaimer flashed saying that Valtrex has only been tested in heterosexual couples. Honestly, I can't see a difference. It's not like a virus such as Herpes is going to care if you're male or female, right?
I was just curious what any potential difference would be.