as an adult woman who chooses to participate in BBBJ, I know there's a risk.
But the risk is alot smaller than unprotected sex. For one thing alot of viruses that thrive in the genitalia do not thrive in the mouth or stomach. Stomach acid kills quite a bit of what if anything might make it down the throat.
After a bbbj, I brush my teeth and gargle with lysterine, further killing what might if anything might be there.
I've been doing bbbj for over ten years (when I was a civie), and I've never had any std's in my mouth or throat.