The 2007 numbers are from 34 states (and 5 areas) that require reporting. These are the highest infection rate states, but the total for 2007 was probably 63,000 rather than the 42,000 reported.

However, the ratios are probably the same.

half of new transmissions result from gay sex

a third result from straight sex

the rest are injection drug related

It seems in the US that the progression is as I thought in terms of behavior.

IV drug use-receptive anal intercourse–

Well, no. Not exactly.

I think you may be misreading the information. I provided numbers on exposure risk (the likelihood of any particular engagement with an HIV positive person leading to seroconversion).

If you wish to know the transmission rates in the US, here are the stats for 2007:

22,472 (53%) male to male

9,076 (21%) male to female

4,939 (12%) injection drugs

4,551 (11%) female to male

1,260 (3%) both MSM and drugs (exact unknown)

139 (0.3%) perinatal (mother to child)

59 (0.1%) other

IV drug use-receptive anal intercourse–

The surprise is the receptive vaginal intercourse (next), as I had imagined it was much lower (although still lower by a factor of 5 than the above).

Thanks for your effort Timothy…

The numbers are very different if we are talking the US or Africa. Very VERY different. And we must also consider that the strains of HIV are different on the two continents.

So “numbers about the rate of transmission” would be hard to tie down. Here are a few statistics I can toss out off the top of my head…

* Over 90% of HIV infections worldwide are in heterosexuals.

* In the US, there is about a 50/50 split in new infections between straight and gay.

* About half of US new infections are among African Americans

* A 2000 study in Uganda found that rates of male to female and female to male transmission were about the same. However none of the males who were circumcised seroconverted.

More info can be found in a Seattle Public Heath pamphlet that discusses risks, however it appears to be written from a white male American perspective.

I found the following grid on Wikipedia

Estimated per act risk for acquisition of HIV by exposure route (US only)

Exposure Route – Estimated infections per 10,000 exposures to an infected source

Blood Transfusion 9,000

Childbirth (to child) 2,500

Needle-sharing injection drug use 67

Receptive anal intercourse* 50

Percutaneous needle stick 30

Receptive penile-vaginal intercourse* 10

Insertive anal intercourse* 6.5

Insertive penile-vaginal intercourse* 5

Receptive oral intercourse*§ 1

Insertive oral intercourse*§ 0.5

* assuming no condom use

§ source refers to oral intercourse performed on a man

As for female to female transmission, there have literally only been a few cases in which this could have possibly been the transmission route.

The heterosexual transmission from women to men fascinates me…as I would not expect that.

Do you have any numbers about the rate of transmission:

female to male, vaginal intercourse

male to female, vaginal intercourse

male to female, anal intercourse

male to male, non-anal intercourse

male to male, anal intercourse

female to female.

I would assume the the numbers are higher for male to female anal intercourse, male to male anal intercourse, male to male non anal intercourse, female to male vaginal intercourse, female to female (these are listed in descending order).

Forgive me if I get a bit graphic.

Your assumption is correct. The 50% reduction studies related to men receiving the virus from infected women via heterosexual vaginal intercourse.

Some nutcase in the US compared infection rates in gay men in the US and found that there was no significant difference between circumcised and uncircumcised. They concluded that “circumcision doesn’t factor into HIV transmission in gay men”. But, stupidly, they made no effort to determine whether or not the gay men engaged in receptive anal sex and it should be pretty obvious that if one is being penetrated, it’s not going to make much difference whether or not they still have foreskin.

We don’t know whether the circumcision of the insertive party during anal sex has any impact on transmission from the receptive partner to the insertive partner. We do know, however, that there are very very few cases of HIV transmission to the insertive party in the US. VERY few.

This may be for a number of reasons: 1) HIV may be easier to transmit from a woman to a man in vaginal sex than to an inservite partner in anal sex, perhaps due to presence in either the vaginal or anal cavities. 2) gay men may generally be more conscious of issues of cleanliness prior to anal sex than women are prior to vaginal sex. 3) most Americans men are circumcised and circumcision may play a part.

We just don’t know.