Continued from Part 1.
If you've just joined us, we're giving a good fisking to the Mayo Clinic's worthless list of STD risk factors, namely:
Having unprotected sex.
Having sexual contact with multiple partners.
Abusing alcohol or using recreational drugs.
Being an adolescent female
The biggest proof that their advice is completely worthless comes from the full description of the first point, 'having unprotected sex'. At a very minimum, they don't make the most minimal distinction between vaginal, anal and oral intercourse. But even within that, the whole thing is basically a ridiculous scare campaign:
Vaginal or anal penetration by an infected partner who is not wearing a latex condom transmits some diseases with particular efficiency. Without a condom, a man who has gonorrhea has a 70 to 80 percent chance of infecting his female partner in a single act of vaginal intercourse. Improper or inconsistent use of condoms can also increase your risk. Oral sex is less risky but may still transmit infection without a latex condom or dental dam. Dental dams — thin, square pieces of rubber made with latex or silicone — prevent skin-to-skin contact.
This one I know is in the 'deliberately misleading to fool the public' category. You know why? Because they use the weasel words 'some diseases'. They then back it up with the gonorrhea example, where one-off unprotected vaginal transmission rates are high. But people don't generally stay up late at night freaking out about getting gonorrhea, do they? As a matter fact, you don't hear about it much, because it can be treated with antibiotics. What people actually worry about the most is HIV. Why not tell them about that instead?
So what are the chances of HIV transmission from unprotected vaginal intercourse with someone who is HIV positive? This is such a classic that I want to put the answer (and the rest of the post, which gets even more awesome by the way, though you may not believe it's possible) below the jump. Suppose a man and a woman have unprotected vaginal intercourse once.
a) If the man is HIV positive, what is the chance the women contracts HIV?
b) If the woman is HIV positive, what is the chance the man contracts HIV?