If you're in combat, when are you going to have time to have sex or even think about it? My main goal would be to destroy my enemy.
*edit* Joe..they perform a VERY thorough physical at the main recruiting office before you ship out. They'd know if you had AIDS or not, and if you did, you wouldn't be joining. They disqualify people for all kinds of reasons, like diabetes, asthma, even calcium deposits. This girl in my platoon had to get a height waiver because she was only 4'9" to get in. They're VERY strict about stuff like that.