The Source

ABC News has a report on a study that has determined the source of HIV/AIDS. No, it wasn't a plague sent by God.

WASHINGTON, May 25, 2006 (AP) — Twenty-five years after the first AIDS cases emerged, scientists have confirmed that the HIV virus plaguing humans really did originate in wild chimpanzees, in a corner of Cameroon.

God damn monkeys.

But check out how long ago it happened.

"The genetic similarity was striking," Hahn said. The first human known to be infected with HIV was a man from Kinshasa in the nearby country of Congo who had his blood stored in 1959 as part of a medical study, decades before scientists knew the AIDS virus existed.

Presumably, someone in rural Cameroon was bitten by a chimp or was cut while butchering one and became infected with the ape virus. That person passed it to someone else.

The Sanaga River long has been a commercial waterway, for transporting hardwood, ivory and other items to more urban areas. Eventually, someone infected made it to Kinshasa.

That's amazing. The first known infection was in 1959? Holy cow. And it all started with one person who had the misfortune of mixing blood with the wrong monkey, and now more than 45 years later, 25 million people are dead.

Another thing that occurred to me is just how interconnected people really are. In one way or another, we've all likely had sex with millions of human beings through the sharing of body fluids. Think about it. One man became infected 45 years ago, and as of today, 65 million people have become infected. That means that one mans body fluid has been passed on millions and millions of times, to the point where I'm sure each of us has come into contact with him.

Now - that's just for human to human contact that resulted in actual HIV transmission. Consider the odds of sexual contact resulting in an infection. These statistics assume un-safe sex where indicated *.

Estimated per act risk for acquisition of HIV by exposure route[39]

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

Blood Transfusion 9,000
Childbirth 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

Now, keep in mind I'm not advocating any kind of un-safe sex of any sort. I'm just using statistics to illustrate a point of human interconnectedness.

Notice the actually low chance a person can become infected due to un-safe sex with an infected partner. The highest possible chance of sexual infection is .5%. This means that a person would have to engage in unprotected "Receptive anal intercourse" 200 times with an infected partner before meeting the odds of becoming infected.

Of course, the highest number of infections are a result of heterosexual sex, and the chance for infection is lower per each sexual contact. It's roughly 5 times less likely. So, I'm going to estimate here based on those statistics and say that the chance of infection from un-safe sex with an infected partner per 10,000 acts is 15. So, we have 65 million infected people to date. At the .15% chance to become infected, that means that it took roughly 4.3 billion sex acts in the last 45 years, with at least 1 partner infected with HIV, to result in 65 million infections.

So, consider that sex acts with infected partners represents a tiny fraction of the total sex acts. There's a lot of sex going on. That's why it seems like the odds of becoming infected are so great. A person could go a lifetime only have the most risky sex possible with only infected partners and they'd likely never get infected. However, somebody has to get infected right? Those that did got really unlucky in a number of ways.

The low rate of infection explains why it took from 1959 until 1981 before the disease was even classified. If the average rate of infection were more like 25%, the planet would be over run with infections to the point of possible destruction. But consider, if there is another lethal virus lurking with half the rate of infection of HIV, it could be spreading through the world populations right now, undected just as HIV was.

In the end, we've all had sex with that first guy that got infected by the monkey in 1959, or pretty much anybody else that lived 50 years ago. We've had sex with somebody, who had sex with somebody else, who had sex with somebody else.. and you multiply that billions of times, where I suspect that if you do the math (I'm not going to, this bit made my head hurt already) each one of us has had sex with every person who lived on the planet 100 years ago.. maybe less. It grows exponentially, and because there has never been a human mass extinction, it carries on all the way to the day of the pre-human ancestors.