I am curious about the 0.2% figure. I have heard it before (even heard it being sworn to in court) but I would like to know how reliable such a figure is, or could be. It seems to me it would necessarily depend on reported rates of intercourse from patients, which is likely to be wildly unreliable. And this figure does not seem to differentiate among the various types of sexual activity which are believed to have different rates of infection - anal intercourse, vaginal intercourse, oral sex, etc. Any body got any good data on how reliable this figure is?
I was imprecise - my understanding is that HIV infection is a direct correlation with viral load. A person who has sex with an HIV+ person just once has a very small chance of being infected; a person who has sex multiple times with one or many HIV+ people has a greater chance, as does someone who shares infected needles with someone HIV+, as the viral load they are exposed to is much much higher. Blood transfusions with HIV+ blood have a much higher level of virus load so are much more likely to cause infection. Finally, people can be asymptomatic and virus-free according to tests for 6-12 months before suddenly showing positive and showing symptoms; it’s not beyond the realms of possibility that some people will show asymptomatic for much much longer.
Naturally there are no really effective studies of ‘how much does it take’ for humans for medical ethics reasons, but my understanding is that this is backed up with research in chimpanzees on HIV-1.
I think we have a pretty good concept of the whole “emerging diseases from Africa” thing. Ebola, Marburg, etc. have pretty similar patterns. It could be that HIV has some completely different thing going, but chances are it emerged much like these other viruses.
Some things to keep in mind is that part of why these diseases emerge is that the forest is being cleared. Humans are beginning to live in places that were previously uninhabited. And because of the food situation (farming is tough in the rainforest, game is plenty), they begin eating species they previously didn’t eat and this means close bloody contact with wild animals. This makes it easier for diseases to cross over. All of this is a recent event, fueled by stuff like logging.
Another is mobility. I think it’d be very difficult for a disease to cross the sahara before modern times. Nobody lives there. Next to nobody crosses it.
Finally, people in villages notice when ALL of somebody’s wives die of some wierd disease. AIDS leaves a pretty specific pattern.
Your tone is to play everything you’re saying down, but you’re saying some interesting shit.
Look, even if aids hasn’t been “a major plague that’s occured many times caused by the same organism,” a lot of other, just as interesting, things could be going on. It looks like we know so little about immunity in populations and viruses and–microevolution–and all that’s being hidden by the attitude “eh, it’s just random. viruses appear like beta particles.”
At least in the case of the suggested 1959 Manchester victim, the identification of HIV in the samples was retracted by the original researchers in 1996. This 1995 newspaper article by Steve Conner is non-technical, but gives a fairly detailed account of how worries had surfaced that the result had been produced by accidental contamination in the lab. All professionally settled without any apparent acrimony between the scientists involved.
Hmm, the story is pretty bizarre. The experiment was carried out in perfect procedure, but the samples that were used later turned out to belong to a contemporary AIDS patient, not the man under investigation. How they were mixed up or who switched them, no one knows. Hence the significance of bonzer’s “professionally settled without accrimony”… swept under the rug? >=)
The article also mentions that many people think that a trial of a polio vaccine in the Congo made from monkeys was the mechanism by which SIV transformed into HIV. What’s the dope on that?
Not sure there’s any real grounds for calling the story “bizarre”. The original researchers knew that PCR might inflate any contamination into an apparent positive result, so had taken what they thought were stringent precautions to minimise that risk. There was no doubt some consternation on their part when the later attempt at replication failed and they were probably initially reluctant to accept that. But they publically acknowledged that the new techniques gave a more convincing result and formally retracted the paper. The matter was widely discussed at the time, not because there was any controversy or accusations flying about, but because the original story had been very high profile itself.
Nor is there any particular reason to expect that the source of the contamination should have ever been publically nailed down. It’s possible that someone eventually traced who that was from, but this probably wouldn’t have been a publishable result once the paper had been retracted. Of some curiosity perhaps, but merely the nailing down of an incidental obscure historical detail about an abandoned claim. Just because something remains unknown or even unpublished doesn’t necessarily indicate a cover-up.
Later experiments refuting a striking earlier claim and the scientists involved accepting the improved data? A nice example of how these things are meant to work, surely?
Doesn’t follow… the black death and other epidemic plagues disappeared for reasons still not understood. The most recent Spanish flu epidemic in 1917-18 was something related to H5N1, but what’s it been doing the last 90 odd years? I guess what I’m suggesting is that HIV may possibly be the offspring of a similar way older virus. The lack of reliable historic information from its source origins makes it hard to say.
That’s what I was thinking, the mobility thing. If it wasn’t able to travel far and just lingered in isolated populations it could be older than we think. I disagree that AIDS leaves a specific pattern though, without modern medicine I would think the presented symptoms to be fairly varied and doctors of the day would more likely have attributed it to the diseases they knew?
To be clear, I’m not at all doubting the HIV-AIDS connection or that HIV causes AIDS or anything, I’m just curious about the age of the virus.
You didn’t read your own article carefully.
It wasn’t just PCR contamination.
I thought I read somewhere that AIDS was possibly traced back to the 1920s-was I wrong?
A paper in Science back in 2000 used phylogenetic methods to trace the common ancestor of the current strains to 1931 plus or minus quite a bit. Link to abstract . I only know this because there’s a possibility that, for my masters thesis, I’ve got to do their analysis over again, but better! 
That’s all I know at the mo though, trying to get in touch with the project supervisor and big exam in three days graaaagh.
Haven’t seen this one corroborated yet.