The Other Thirty Percent

I’m watching the Cubs - Zambrano just had a nice 1-2-3 inning - and in between the top and bottom of the first inning is a commercial for a drug for genital herpes.

One study found that up to 70% of people who had genital herpes got it from their partner when they had no signs of an outbreak.

So, what I want to know is: What about that other 30%? Did they just not notice? Were they drunk? Or is there some sort of oozing-sore fetish I haven’t heard about?