PLEASE READ THIS.
HIV is transmitted from a woman to a man during BBF when vaginal fluid from a woman enters through your pea hole. Your pea-hole is a mucus membrane and HIV can penetrate that. The other reason is if you have any laceration on your genital, hiv can easily get into your body. All HIV needs is an exposed white blood cell to attach itself onto.
Going to DATY, first thing your mucus memberane in your mouth is similar to the pea hole mucus. As you can clearly see during DATY your mucus membrane can get into contact with vaginal fluids, hence allowing access for HIV to enter your blood stream through mucus membrane. The other is you may have brushed your teeth (or for whatever reason) and unknowingly scratched your gum or any part of your mouth that may have tiny invisible lacerations. This also facilitates access for HIV into your blood stream.
DATY IS NOT SAFE. Many people think it is safe because many of the ladies they had encounter with are not
infected.
for more info
http://www.cdc.gov/hiv/resources/qa/qa19.htm