# How is HIV actually transmitted? **URL:** \ **Category:** Factual Questions\ **Created:** [March 16, 2005, 9:39am UTC](https://boards.straightdope.com/t/how-is-hiv-actually-transmitted/294792 "2005-03-16T09:39:57Z")\ **Posts on this page:** 10\ **Page:** 1
**Author:** ![antechinus](https://avatars.discourse-cdn.com/v4/letter/a/fbc32d/32.png) [@antechinus](https://boards.straightdope.com/u/antechinus)\ **Post date:** [March 16, 2005, 9:39am UTC](https://boards.straightdope.com/t/how-is-hiv-actually-transmitted/294792/1 "2005-03-16T09:39:57Z")
[This thead](http://boards.straightdope.com/sdmb/showthread.php?p=5952554) reminded me of a question I have always wondered - how does the HIV virus get from person A to person B. Easy to understand for injecting drug users - infected blood is directly injected into the bloodstream. Easy to understand for anal sex, for the ‘recipient’ - infected semen may enter small cuts or abrasions in the rectum. Even understandable in vaginal sex for the same reason. But what about for the …um…‘provider’ of said semen in both vaginal and anal sex? Unless the penis has cuts on it how could the virus possibly pass through the skin? It is just like if someone bled onto your skin who was infected. My understanding was that the virus does not pass through the skin. ---
**Author:** ![Skellington](https://avatars.discourse-cdn.com/v4/letter/s/94ad74/32.png) [@Skellington](https://boards.straightdope.com/u/Skellington)\ **Post date:** [March 16, 2005, 1:12pm UTC](https://boards.straightdope.com/t/how-is-hiv-actually-transmitted/294792/2 "2005-03-16T13:12:32Z")
In a situation like this the issue is that normal skin is different from mucous membranes. A lot can pass through mucous membrane that cannot pass through normal skin. This may not be the whole answer but I hope it makes thing a little clearer. ---
**Author:** ![Smeghead](https://avatars.discourse-cdn.com/v4/letter/s/f1d935/32.png) [@Smeghead](https://boards.straightdope.com/u/Smeghead)\ **Post date:** [March 16, 2005, 8:31pm UTC](https://boards.straightdope.com/t/how-is-hiv-actually-transmitted/294792/3 "2005-03-16T20:31:49Z")
It’s not at all unusual for a man to have microscopic cuts on his penis that are so small he doesn’t even know they’re there. ---
**Author:** ![ouryL](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ouryl/32/6067_2.png) [@ouryL](https://boards.straightdope.com/u/ouryL)\ **Post date:** [March 16, 2005, 8:36pm UTC](https://boards.straightdope.com/t/how-is-hiv-actually-transmitted/294792/4 "2005-03-16T20:36:45Z")
> [@Smeghead](#): > > It’s not at all unusual for a man to have microscopic cuts on his penis that are so small he doesn’t even know they’re there. Damned teeth!! :eek: ---
**Author:** ![ouryL](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ouryl/32/6067_2.png) [@ouryL](https://boards.straightdope.com/u/ouryL)\ **Post date:** [March 16, 2005, 8:38pm UTC](https://boards.straightdope.com/t/how-is-hiv-actually-transmitted/294792/5 "2005-03-16T20:38:52Z")
> [@ouryL](#): > > Damned teeth!! :eek: I fergot!! :smack: Damned teeth!! :eek: ---
**Author:** ![antechinus](https://avatars.discourse-cdn.com/v4/letter/a/fbc32d/32.png) [@antechinus](https://boards.straightdope.com/u/antechinus)\ **Post date:** [March 21, 2005, 12:19am UTC](https://boards.straightdope.com/t/how-is-hiv-actually-transmitted/294792/6 "2005-03-21T00:19:49Z")
> [@ouryL](#): > > I fergot!! :smack: > > Damned teeth!! :eek: Something about that URL tells me it is not work safe. I don’t think I will open it. > [@Smeghead](#): > > It’s not at all unusual for a man to have microscopic cuts on his penis that are so small he doesn’t even know they’re there. Not unusuall?!! Sounds unusual to me. Is all skin like this, or just penis skin? Not that I don’t believe you, but do you have a cite? ---
**Author:** ![CC](https://avatars.discourse-cdn.com/v4/letter/c/f1d935/32.png) [@CC](https://boards.straightdope.com/u/CC)\ **Post date:** [March 21, 2005, 2:42am UTC](https://boards.straightdope.com/t/how-is-hiv-actually-transmitted/294792/7 "2005-03-21T02:42:14Z")
It would also seem that the urethral mucosa provides an easier route to the bloodstream of the man than the skin on the outside of the penis, and that may also come in contact with HIV that the female or the male is carrying. Or, vice versa, actually. If you can get that buring sensation from soaping up too vigorously in the shower, then it can’t be too hard for microbes to make their way into that same viciinity. ---
**Author:** ![Otto](https://avatars.discourse-cdn.com/v4/letter/o/bbe5ce/32.png) [@Otto](https://boards.straightdope.com/u/Otto)\ **Post date:** [March 21, 2005, 3:14am UTC](https://boards.straightdope.com/t/how-is-hiv-actually-transmitted/294792/8 "2005-03-21T03:14:48Z")
> [@antechinus](#): > > Not unusuall?!! Sounds unusual to me. Is all skin like this, or just penis skin? Not that I don’t believe you, but do you have a cite? [Will this do?](http://www.thebody.com/Forums/AIDS/SafeSex/Archive/TransmissionSexual/Q9164.html) > [@Rick Sowadsky](#): > > During unprotected intercourse, there can be small microscopic cuts and tears on the head of the penis, and the virus can enter your body through these tiny tears. The head of the penis is a mucous membrane, and is especially prone to microscopic tears and abrasions during sexual intercourse. ---
**Author:** ![davenportavenger](https://avatars.discourse-cdn.com/v4/letter/d/5f8ce5/32.png) [@davenportavenger](https://boards.straightdope.com/u/davenportavenger)\ **Post date:** [March 21, 2005, 3:28am UTC](https://boards.straightdope.com/t/how-is-hiv-actually-transmitted/294792/9 "2005-03-21T03:28:51Z")
No cite, but I’ve heard that female-to-male vaginal transmission is the most unlikely route of infection. It still happens, of course, but it’s a lot rarer than other avenues since the tiny tears on the penis have to connect with tiny tears on the vagina to make infection possible. Same goes for anal sex where the receiver is the infected partner, though I think it’s more likely in that case since there are more tears and places where the blood can get through. ---
**Author:** ![Loopydude](https://avatars.discourse-cdn.com/v4/letter/l/e56c9b/32.png) [@Loopydude](https://boards.straightdope.com/u/Loopydude)\ **Post date:** [March 21, 2005, 4:03am UTC](https://boards.straightdope.com/t/how-is-hiv-actually-transmitted/294792/10 "2005-03-21T04:03:43Z")
In the case of vaginal sexual intercourse, barring direct blood-semen contact through some sort of lesion, the most importasnt route of infection is through a class of antigen-presenting cells referred to as dendritic cells (commonly known as Langerhans cells), which reside in genital epithelia (esp. cervical and vaginal mucosa). These cells present a variety of receptors for HIV binding, and their job is to move foreign proteins quickly from where they are encountered to where they can be presented to the immune system, by migrating from the epidermis to the lymph nodes. The cells are not lysed by HIV infection like T-Cells, but still can harbor the virus and allow its replication. As such, they provide an insidiously efficient route of entry, a sort of Trojan Horse, delivering a concentration of virus to more of the very sorts of cells it infects.