Hi Dr. Ill describe my particular experience: I was at my friend's house, my friend masturbated and ejaculated, I didn't touch him. My friend went to the bathroom but I don't know what he did there. We went to my house, the trip lasted approximately 20 minutes by car. When we arrived at my house, we both got into the shower, water had already fallen on us when my friend inserted a finger into my anal cavity. I was then very worried. if some semen remained on his finger at that point could be risky for me to get hiv?

Welcome to our Forum. Thanks for your detailed description.  The events you describe DID NOT put you at risk for HIV or any other STI.  STIs are harder to transmit that you think.  They require DIRECT contact with a site of infection and are not transmitted through indirect contact.  Exposure to the air and environment makes HIV and other STIs non-infectious almost immediately.  For this reason the CDC, the WHO and all experts agree that even mutual masturbation in which partners get each others secretions directly on each other is a no risk event.  Your exposure was far less risky than that.---

Dear Dr.

Absolutely,  Persons with a negative test for HIV cannot transmit the infection.  This just strengthens the fact that you are at no risk.  No need for testing and certainly no need for concern.  EWH ---

Thanks so much Dr. I really appreciate it!

Dear Dr. 

Even if he were infected, his RNA test would be positive.  Further, typically, when persons start PrEP, they are tested to prove that they are not infected.  This is further evidence that you are not at risk for HIV from this encounter.---