Your risk of contracting an STI from this type of encounter would be very low. First, the escort would have to have the infection. If she were clean, as many are, you obviously would not need to be concerned at all. That said, even if she were infected with something, the risk would be low from oral sex, particularly for HIV, and not much higher from vaginal sex with a condom, as there is minimal to no exchange of bodily fluids. Most in this situation will test after a few weeks just to be sure, but I see no reason to be concerned given your desciption of the encounter.
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