HIV Risk Transmission by Sex Act

[Sweet Emily J 172062]

 

- The risk estimates for the sexual transmission of HIV, per sex act, range widely, from:

- 0.5% to 3.38%... for receptive anal intercourse;

- 0.06% to 0.16% for insertive anal intercourse;

- 0.08% to 0.19% for receptive vaginal intercourse (i.e., male-to- female); and - approximately 0.05% to 0.1% for insertive vaginal intercourse (i.e., female-to-male).

 

The risk of transmission from unprotected oral intercourse (whether penile-oral or vaginal-oral) is markedly lower than for anal or vaginal intercourse, and findings suggest a low but non-zero transmission probability.

 

Vaginal Intercourse

 

"The risk estimates of HIV transmission from receptive vaginal intercourse (i.e., risk to the female partner) range from 0.08% and 0.19%. The risk for insertive vaginal intercourse (i.e., risk to the male partner) has been estimated to be slightly lower, with estimates ranging from 0.05% to 0.1%...the risk of sexual transmission among heterosexuals was reported as 1 to 2 cases per 1,000 sex acts (or roughly 0.1%)"/I]

 

 

I am not advocating truth or falsehood within any of these statistics, BUT, just to be clear and so that the statistics are being interpreted properly; all of the statistics from these studies are based on the fact that one partner is actually HIV positive.

 

For example for the high risk activities:

 

For every 1000 times someone who is HIV positive has unprotected vaginal sex with another person, on average they may transmit the disease 1-2 times to their partner. It is NOT saying that for every 1000 unprotected vaginal sex acts, 1-2 people contract HIV.

 

And when someone performs unprotected anal sex on a partner who is HIV positive, there is a 0.06% to 0.16% chance that the person inserting will contract the disease from the HIV positive receiver.

 

The studies assessed the ability and risks of transmission, and concluded that there is a x.xxx% chance of contracting HIV when engaging in those specified unprotected sex acts with a person who is in fact HIV positive.

 

They are not overall blanket stats to say that for every single unprotected sex act that occurs between any two people, there is a x.xx% chance of contracting HIV.

[Guest *l**e]

just an FYI, most of these studies (in the small print) recognize lying as a factor that may skew data.

 

for example, a "heterosexual male" may lie about having had a homosexual encounter. Or a female may lie about having received anal sex. I know it seems kind of dumb to many of us that someone would lie in this situation, but some independent studies have shown that as many as 85% of respondents lie on these HIV type study surveys.

 

There are a great many scientists and HIV doctors that feel it may in fact be impossible for a male to contract HIV via vaginal sex with a woman unless he has cuts or abrasions on his penis.

 

I am in no way suggesting this is fact, I'm just trying to point out that even the best studies have flaws that are almost impossible to control.

[Sweet Emily J 172062]

just an FYI, most of these studies (in the small print) recognize lying as a factor that may skew data.

 

for example, a "heterosexual male" may lie about having had a homosexual encounter. Or a female may lie about having received anal sex. I know it seems kind of dumb to many of us that someone would lie in this situation, but some independent studies have shown that as many as 85% of respondents lie on these HIV type study surveys.

 

There are a great many scientists and HIV doctors that feel it may in fact be impossible for a male to contract HIV via vaginal sex with a woman unless he has cuts or abrasions on his penis.

 

I am in no way suggesting this is fact, I'm just trying to point out that even the best studies have flaws that are almost impossible to control.

 

Exactly. Thank you for pointing this out. These studies are very unscientific just for that reason that they are entirely based on self reporting from the subjects involved.

 

I also wanted to point out that it was mentioned in that link that 44% of new HIV cases in Canada within the time frame of the studies were among homosexuals. Considering that not 44% of Canadians are homosexual, it is clear that even taking into consideration a +/- in reporting errors, the prevalence of this disease is higher among homosexuals, and it is not simply a homophobic stereotype as was stated in another thread.

[fortunateone 156618]

It is possible the infection rate is higher for two reasons: they have sex in a higher risk category (bb anal) and second that they are getting tested in the first place.

 

There also appears to be some evidence that there are a high number of people who are infected but don't know it, and that this is in the younger population. We do see studies that show that the highest incidence of chlamydia appears to be in the 14-20 year olds. I would think that a 15 or 17 year old is unlikely to tell their parents they need a full STD workup when going to the doctor.

[funstuff 100]

An interesting reply. Thanks.

[cyclo 30131]

When AIDS was first discovered homosexual men, hemophiliacs (due to infected blood transfusions), intravenous drug users and Haitians (Haiti is where the HIV virus first arrived in North America from Africa) were the four groups affected. Since then the proportion of male and female heterosexuals affected by HIV has increased.

 

"When HIV reporting began in 1985, men who have sex with men (MSM) accounted for over 80% of all cases. Although MSM is still the predominant exposure category, the proportion has decreased significantly over the years. In 2010, 47.6% of all positive adult HIV cases with known exposure category were attributed to MSM.

 

Heterosexual contact, at 30.8% of case reports among adults in 2010, was the second most reported exposure category (13.2% attributed to having sexual contact with someone with no identified risk, 11.0% attributed to having sexual contact with a person at risk, and 6.6% to those of origin from an endemic country)."

 

Source: Public Health Agency of Canada report "At A Glance - HIV and AIDS in Canada: Surveillance Report to December 31,2010"

 

There is far less social stigma attached to identifying as homosexual today than there was in the late seventies and early eighties when AIDS symptoms and HIV were first being discovered. The increase in heterosexual cases is therefore unlikely to be based upon a larger number of people being embarrassed to say they have had sex with other men.

 

It is more likely that more heterosexuals are engaging in the highest risk behaviour for transmission... unprotected anal sex. I'm sure many of the women on this board can attest to the increased interest, requests and curiosity from their clients regarding Greek services. (I realize that no one on CERB would offer bare back anal and I'm not suggesting that.) So regardless of whether you're gay, bi, bi-curious, transgendered, heterosexual or got drunk one night and took a walk on the wild side... the sexual practice of unprotected anal intercourse (being the receiver) is your highest risk for HIV transmisssion.

 

In the early days of AIDS it was possible for heterosexuals to feel complacent, immune or at extremely low risk of contracting HIV. As heterosexual behaviour changes, the risk increases and the number of infections increases.

[Phaedrus 209521]

Thanks for doing the work to collect this stuff together, cyclo - much appreciated! I know that digging all this stuff up takes significant effort.

 

One thing I do want to address, though, is the relative reliability of the science here. There's a huge problem with this kind of thing is that the relative risk of particular acts is almost impossible to establish. Many people who have acquired HIV probably can't tell you with any certainty who they got it from, never mind shed any light on what they may have been doing at the time, and discounting for the moment that most of us probably don't limit our sexual interactions to just one way of having fun. And that's before you have to account for the fact that people may indeed lie, or simply misremember things without any actual attempt at malice.

 

Unfortunately, you can't actually do proper, scientific experiments on this stuff; you just can't take a thousand HIV+ guys, and have a thousand uninfected people give them one BBBJ each, and then see how many are infected in turn. And so we have to make the best of what we have available, and study the ferociously complex mess that is real life for real people and make the most sense of it that we can. And so, yes, there will always be a margin of error; frequently it'll be a very large margin for lots of different errors. What's as important as anything else is for studies to be honest about the assumptions they've made, about the flaws in their methodology, and the limitations of the available data sets.

[SamanthaEvans 166766]

Cyclo, I, too, am grateful to you for providing this overview. Thank you for taking the time and for having the care to show what you've learned.

 

Two things occur to me, in addition to the good points already raised by others about interpreting those percentages and the reliability of reporting rates. First, the B.C. Centre for Disease Control estimates that there are about 3,500 people in B.C. who are unknowingly infected with HIV. That's a lot of people. The Vancouver General Hospital did a year-long study that concluded in 2012 in which they offered HIV testing to anyone who was having blood tests for any reason instead of focusing on people in high-risk groups, primarily IV drug users and gay men. In one year, more than 30 people were diagnosed HIV+ and VGH estimated that at least 10 of those would not have been diagnosed otherwise within that time.

 

Focusing on people in designated high-risk groups isn't adequate. True, the discovery of 30 or so infected people is fairly small, given that VGH is an enormous teaching hospital that conducts many, many thousands of blood tests every year. Nevertheless, early detection of HIV makes treatment much more effective than diagnosis after someone has symptoms of full-blown AIDS.

 

As for honesty about homosexual contact, this is a more difficult matter than it may seem at first. A significant number of men who are involved in sexual relationships with women also engage in sexual activities with other men. They don't always inform their female partners that they participate in homosexual acts. A lot of them don't admit it to themselves, either.

[cyclo 30131]

Samantha raises a good point about who is and isn't getting tested.

 

In addition to "who" gets tested, "when" you or your partners get tested is also critical for managing risk. HIV is most cantagious during the early stages of infection. In the first 8-12 weeks after being infected, a person has more of the virus in their blood because their immune system hasn't had a chance to fight back yet. (The virus peaks again to similar levels in the late stages of AIDS after the body's immune system has essentially been defeated.) If you are engaging in the high risk sex acts identified in the first post, frequent testing will not reduce your risk of becoming infected, but it will reduce the risk of you infecting your partners if you've become infected.

 

Additional Comments:

Many people who have acquired HIV probably can't tell you with any certainty who they got it from, never mind shed any light on what they may have been doing at the time, and discounting for the moment that most of us probably don't limit our sexual interactions to just one way of having fun.

 

I agree it's not easy. Most researchers seem to acknowledge this also. A research article in the the Journal of Acquired Immune Deficiency Syndromes entitled "Heterosexual Transmission of HIV-1 is Associated with High Plasma Viral Load Levels..." states "Risk factors for heterosexual transmission of HIV are not fully understood. In fact a proportion of people with sexual exposure to HIV remain uninflected despite multiple and continuous intercourse with HIV infected partners." In part this goes to show that where risk/probability is involved, you can't say with certainty what will happen to a specific individual, only what can happen in a larger population. Just like the link between smoking and cancer. We know many people will be affected, but we don't know which individuals. We've all seen the harty pack a day smoker.

 

Unfortunately, you can't actually do proper, scientific experiments on this stuff; you just can't take a thousand HIV+ guys, and have a thousand uninfected people give them one BBBJ each, and then see how many are infected in turn. And so we have to make the best of what we have available, and study the ferociously complex mess that is real life for real people and make the most sense of it that we can. And so, yes, there will always be a margin of error; frequently it'll be a very large margin for lots of different errors. What's as important as anything else is for studies to be honest about the assumptions they've made, about the flaws in their methodology, and the limitations of the available data sets.

 

Experiments are definitely out of the question, but there are some studies that are pretty close. In this particular study they followed 38 heterosexual couples in which one partner was infected and the other wasn't and who continued to have unprotected sex!!!! "... despite intensive counseling and behavioral intervention." (This is just another example that knowledge alone doesn't necessarily eliminate risky behaviours.) The frequency and type of unprotected sex acts and occurence of other STI's wasn't significantly different for the couples. The most significant factor in determining which uninfected partners became infected was the "viral load" (amount of infection in the blood) of the originally infected partner.

[Serena Blake 14066]

well either way I still say with my body so sensitive to everything and my poopy luck I would catch something

 

lol I got pregnant with my son the 1 time i didn't use a condom

 

there was actually a story on the news a while ago that there has been an aids spike here in Moncton linked to anonymous sex from websites. Things SHOULD be protected!! you can look at the numbers all you want sometimes your number is just up and it is not your day. "It won't happen to me" is always a thought until something happens ;)