The statistics found online are quite normally exaggerated, even from the CDC. Many doctors who specialize in this say the things one should look out for with BBBJ are Gonorrhea, NGU (normally caused by Chlamydia but nearly impossible to get via BBBJ), and Herpes. Most Gonorrhea will produce secretions in a matter of days, and the risks of Herpes are minimal without open sores.
The risk is there, just not as much as many make it to be. And if you have something, chances are you'll produce symptoms.