Specific Sexual Practices: What are the Risks?
Studies have repeatedly demonstrated that certain sexual practices are associated with a higher risk of HIV transmission than others.
Vaginal Intercourse:
Unprotected vaginal intercourse is the most common mode of HIV infection worldwide. In the United States and many other developed nations, it is the second most common mode of sexual HIV transmission (after anal intercourse among MSM).
At least five European and American studies have consistently demonstrated that male-to-female HIV transmission during vaginal intercourse is significantly more likely than female-to-male HIV transmission. In other words, HIV-positive men are much more likely to transmit the virus to HIV-negative women through vaginal intercourse than HIV-positive women are to HIV-negative men.
There are a few reasons for this. First, there are more men than women in the United States infected with HIV, meaning that it's much more likely for a female to have sex with an HIV-positive male than for a male to have sex with an HIV-positive female. Second, women have a much larger surface area of mucosal tissue – the lining of the vagina and cervix that can chafe easily and are rich in immune system cells that can be infected by HIV – than men. For men, HIV must enter through a cut or abrasion on the penis, through the lining of the urethra inside the penis.
There has been some research suggesting that men who are uncircumcised have a higher risk of becoming infected with HIV or transmitting the virus if they are already HIV positive. However, it is important to stress that men who are circumcised can still be infected (or transmit the virus) if condoms are not used for vaginal sex.
Men or women who have ulcerative sexually transmitted infections (STIs), such as genital herpes or syphilis, are more likely to spread the virus if they are HIV positive or to become infected with the virus if they are HIV negative.
Anal Intercourse:
Being the receptive partner – the "bottom" – during unprotected anal intercourse is linked to a high risk of HIV infection. The reason for this is that HIV-infected semen can come into contact with mucosal tissues in the anus that can be damaged easily during anal intercourse. And the risk of HIV transmission isn't necessarily reduced if the "top" pulls out before ejaculation – studies have demonstrated that pre-ejaculate (pre-cum) can contain high amounts of HIV and can result in transmission during anal intercourse.
It's important to note that both MSM and heterosexuals have anal intercourse. Many heterosexuals report that it is a pleasurable form of intimacy that eliminates the risk of pregnancy. However, it is still associated with a high risk of HIV infection, if condoms are not used and the insertive partner's HIV status is either positive or not known.
Is the insertive partner (the "top") also at risk during unprotected anal intercourse? At least eight studies conducted over the years were unable to demonstrate a clear link between insertive anal sex and a risk for HIV infection among MSM. However, these studies should not be interpreted to mean that being the top during anal intercourse – and not using a condom – is without risk. We know that men can be infected with HIV through vaginal intercourse – an activity in which they are the insertive partner. Based on this knowledge, it is also believed that the insertive partner during unprotected anal intercourse can also be infected with HIV. Studies, using mathematical estimates, suggest that unprotected insertive anal sex is roughly four to 14 times less risky than unprotected receptive anal sex. However, experts still believe that the risk for transmission is noteworthy.
Penile-Oral Sex
Of the different sex acts, the one that often causes the greatest amount of confusion in terms of risk – and raises the greatest number of questions – is penile-oral sex. The fact is, most experts agree that fellatio, sometimes referred to as "blow jobs," is not an efficient route of HIV transmission. However, this does not mean that it cannot happen.
Research attempting to evaluate the risk of fellatio has often faced important limitations. For starters, very few people participating in studies only engaged in penile-oral sex. Many people also had unprotected vaginal or anal intercourse, making it very difficult to determine if unprotected fellatio is an "independent factor" associated with HIV transmission. There are also people who test positive for HIV and claim that unprotected fellatio was their only risky behavior. However, it's virtually impossible to know if these people are always reporting their sexual behavior accurately. (Study volunteers often have a difficult time admitting the truth about potentially embarrassing behavior to healthcare professionals conducting scientific studies.)
Because unprotected fellatio can mean that body fluids from one person can (and do) come into contact with the mucosal tissues or open cuts, sores, or breaks in the skin of another person, there is a "theoretical risk" of HIV transmission. "Theoretical risk" means that passing an infection from one person to another is considered possible, even though there haven't been any (or only a few) documented cases. This term can be used to differentiate from documented risks. Having unprotected receptive anal or vaginal intercourse with an HIV-positive partner is a documented risk, as they have been shown in numerous studies to be an independent risk factor for HIV infection. Having unprotected oral sex is a theoretical risk, as it is considered possible, but has never been shown to be an independent risk factor for HIV infection in studies.
Here's a good way to think about theoretical risk: In theory, it is possible that while walking down the street, a meteor will fall on your head and kill you instantly. This is because meteors do occasionally fall to earth. People live their lives above ground, so there is a theoretical risk of being hit be a meteor. In fact, there have been reports of a few people being hit by meteors. But because the risk is so small, given that few meteors fall to earth and the large number of inhabitants of this planet, the risk is purely theoretical. The same principle holds true with oral sex – millions of people all over the world are believed to engage in unprotected oral sex and there have only been a handful of documented cases of HIV transmission. In turn, fellatio, and other types of oral sex (see below), remains a theoretical risk for HIV infection.
There have been a number of studies that have closely followed MSM and heterosexual couples, in which one partner was HIV positive and the other partner was HIV negative. In all of the studies, couples that used condoms consistently and correctly during every experience of vaginal or anal sex – but didn't use condoms during oral sex – did not see HIV spread from the HIV positive partner to the HIV negative partner.
There have been three case reports and a few studies suggesting that some people have been infected with HIV as a result of unprotected oral sex. However, these case reports and studies all involved MSM – men who were the receptive partners (the person doing the "sucking") during unprotected oral sex with another HIV-positive man. There haven't been any case reports or studies documenting HIV infection among female receptive partners during unprotected oral sex. Even more importantly, there hasn't been a single documented case of HIV transmission to an insertive partner (the person being "sucked") during unprotected oral sex, either among MSM or heterosexuals.
Is insertive oral sex a possible route of HIV transmission? Yes. But is it a documented risk? Absolutely not.
Oral-Vaginal Sex
Like the study of fellatio, evaluating the risk of unprotected oral-vaginal sex (cunnilingus) is difficult, given that most people surveyed in studies did not avoid other types of unsafe sexual activity. However, there have been case reports highlighting one case of female-to-female transmission of HIV via cunnilingus and another case of female-to-male transmission of HIV via cunnilingus. Both of these cases involved transmission from receptive partner (the one receiving oral sex) to the insertive partner (the one performing oral sex). There haven't been any documented cases of HIV transmission from the insertive partner to the receptive partner.
Oral-Anal Sex
Oral-anal sex is often referred to as analingus. Analingus, or "rimming," is not considered to be an independent risk factor for HIV. However, it has been shown to be a route of transmission for hepatitis A and B, as well as parasitic infections like giardiasis and amebiasis.
Digital-Anal or Digital-Vaginal Sex
Digital-anal or digital-vaginal sex is the clinical term for "fingering" either the anus or the female genitals (including the vagina). While it is theoretically possible that someone who has an open cut or fresh abrasion on his or her finger or hand can be infected with HIV if coming into contact with blood in the anus or vagina or vaginal secretions, there has never been a documented case of HIV transmission via fingering.
Source: http://www.aidsmeds.com
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