precum

Precum is simply that little drop of fluid that sometimes shows up sometimes when a male is aroused - especially if the arousal goes on for quite some time.

I used to conduct safe-sex seminars in my college days for the arriving freshmen, and if they were bold enough the question of sperm in pre-cum would come up. Ideally, there shouldn't be sperm in precum - precum is a product of several glands and is not itself a sperm carrier. The problem is the odds of precum picking up sperm along its way on the urogenital tract, while they're not gambling odds, certainly aren't impossible ones. The more recently the man with the shiny, glistening tip has ejaculated, the greater the chance of some live sperm cells still worming their way around inside - but hell, if he's peed even once since then you just drove the odds down to almost zero. But this is reality and your life - why risk the impossible odds?

Now diseases are a whole different subject, and as you all should know the level of sperm count in a bodily fluid has very little to do with what you can actually acquire from an infected partner. It's not worth it.