Yep. Exposure to body fluids, especially saliva. According to the CDC article you can also get Listeria monocytogenes by eating contaminated food. Lovely.
Way back in my undergraduate Microbiology program we had a mandatory class taught by a statistician on the mathematics of epidemics. Being horny little buggers we were very attentive when the topic came around to STDs. Simply put, promiscuity kills, and however bad you think the chances are, they're worse.
How many waiters, chefs, cooks, are gay?