I had a recent encounter that has been classified as no risk in context of HIV exposure from experts on this site and a couple of other sites which is a great relief and thank you. My incident however have led me to ask questions, purely from trying to establish a better understanding of HIV transmission, but so far my research has failed me. So hoping the good folks here can shed some light on the below.
Before I start, I have thoroughly read through modes of transmission in adults associated with HIV risk i.e. unprotected anal/ vaginal sex, sharing needles with infected people and blood transfusion - These risks are mentioned here and also other reputable sites such as The Body and Poz Forums. I understand and I’m clear on this front and I do not challenge these being the only risks.
My question relates in trying to understand the basic science behind “why and how” HIV lacks transmission under specific scenarios. One of the most popular one being mutual masturbation whereby even when an HIV infected man is using his fresh semen or an HIV infected female is using her fresh cervical/vaginal fluids to masturbate in and around the urethra, this is still generally classified as no risk. In fact on one site, I even read a post which said that if an infected HIV person puts his finger dripped with semen into one’s urethra, this still wont pose as a transmission risk. All this is fine and i’m sure its true and the common reasoning is that HIV doesn’t survive outside the body. This is where things get a bit confusing for me ( and from what i’ve seen, also for many other people).
The logic that plays in my mind is that if in fact the outer protein receptors of the virus do remain effective for transmission (and hence can reproduce) may it be only for a few seconds and given the inside of the urethra does contain the appropriate cells for the virus to latch on to, then how does having fresh semen or cervical fluid (with a high HIV viral load) when rubbed inside and around the urethra does not pose an HIV transmission risk?
I also understand that the virus simply does not infect a person when entering the urethra and that it has to pass through a few different protective layers before being able to attach and replicate itself via the CD4 cells. Also I understand that the area of the urethra makes it difficult for the virus to enter inside the urethra in the first place. However it seems/appears completely plausible based on the above scenario that transmission is still very much possible - So again please help me understand the basic science that renders such a scenario as no risk for transmission?
Apologies for the long message but I think a detailed answer here will greatly assist me and many others who have similar thoughts. Also, happy to be referred to any links as well. Thanks.