However, that does cast a different light on the statistics. I agree that at some point in a long monogamous relationship the non HIV partner will be exposed, but given that infectivity isn't that high, (estimated between 0.005 and 0.009 for male-to-female transmission, and 0.003 and 0.001 for female-to-male transmission for a single instance of unprotected intercourse) cutting down the number of exposures makes a big difference. Which means that a condom, properly used, can prevent infection for a significant number of people.
>> (estimated between 0.005 and 0.009 for male-to-female transmission, and 0.003 and 0.001 for female-to-male transmission for a single instance of unprotected intercourse) cutting down the number of exposures makes a big difference. Which means that a condom, properly used, can prevent infection for a significant number of people. <<
No, it doesn't, because the condom-failure risks are unlinked while the contraction risks are linked. (I don't know if they are completely independent, but there is definitely some linkage.)
See, the reason the infection rate is so low among heterosexuals is because heterosexual sex normally doesn't provide the AIDS virus with a means of getting within the other person's body. There has to be some open wound for the transmission to occur: a laceration, an ulceration, a tear. These breaches in the epidermal integrity are frequently caused if sexually transmitted diseases are present, or if sodomy occurs. But sometimes they just happen for unknown or undetected reasons.
Now, although some people get one-time breaches, the fact is that most breaches are due to some persistent, chronic, or re-occuring condition. So, in most cases the condoms won't make a difference because the AIDS virus wouldn't get transmitted no matter what. In those cases where transmission is possible once, it is very likely that the transmission is possible often.