cyrusabdollahi said:
Hi Tara,
I see where you are going with this, but since I am not a Biology major, please do.
Sure. Many AIDS deniers, for example, use the aforementioned Christine Maggiore's life story as a case in point. She's tested HIV+, but as her organization notes, remains "alive and well." Therefore, HIV doesn't cause AIDS, because she's never developed AIDS.
Of course, if they took a broader picture of infectious disease epidemiology, they'd see how silly this is. With every pathogen known to man (with the possible exception of rabies), we know people who are infected but never develop disease symptoms. Look at tuberculosis, for example--approximately a third of the world is infected with this bacterium. However, only a small fraction of that go on to develop disease symptoms, and only a fraction of those die in any given year. To AIDS deniers, then, because many people carrying TB remain "alive and well,"
Mycobacterium tuberculosistherefore doesn't cause TB, right? Obviously that's incorrect, but that's one of their big arguments against the current "dogma" that HIV causes AIDS.
However, even medical science doesn't say that all people who are HIV+ will develop AIDS. We know of groups of people who have been HIV+ for years, yet are apparently just fine (even without antiretroviral drugs). These are known as "long-term nonprogressors," and are a group that's actively being studied to see just how they're holding the virus in check--what is it about them that keeps them OK, whereas other people succumb in just a few years if they're not treated? Again, where AIDS deniers sees a group like this and goes, "aha! These people aren't dying of AIDS, therefore HIV doesn't cause AIDS!", infectious disease epidemiologists, virologists, and immunologists see this as an expected outcome that we see with every other pathogen, and an opportunity to better understand the host/virus interaction.
Similarly, there are people who are repeatedly exposed to the virus, but never seroconvert. Why not? Deniers again cry foul with regard to HIV causation of AIDS, but meanwhile scientists have found factors (such as a mutation in the CCR5 gene, a protein on cells that helps the virus bind and invade host cells) that make a host resistant to infection in the first place. Again, these are things we'd expect with a broader understanding of infectious disease epidemiology, but deniers (wrongly) think it presents a challenge for the HIV/AIDS paradigm.
What do you say in response to his claim of lots of false positive testing used by clinical researchers in populations that are highly prone to giving false testing results, or the that testing positive for AIDs varies from country to country?
Again, this is something we see with all diagnostic tests (for any illness, be it cancer, infectious disease, autoimmune disease, etc. etc.)--no test is perfect. All have a rate of false positives or negatives associated with them. With HIV, that's why we use an original screening test, followed by a secondary (more specific) test. The first one will weed out most of the people who are negative (and do so fairly cheaply); the second (more expensive) test will confirm those who are positive.
Deniers like to say that there are all these conditions that will result in false positives. And indeed, a number have been reported in the literature--but do they mention that these reports are typically associated with *one case*? So while they say things like "there are 60 different conditions that have resulted in false positive results," that means that there have simply been ~60 (or heck, I'll be generous and even give them a few hundred) people, with certain conditions, whose condition has been associated with a false positive HIV test (and again, I'll note they are *associated* with this result--not necessarily *causal*). It's a big red herring, because again, we see this with pretty much every diagnostic test. But the HIV test is given to tens of millions of people, and the error rate is very small overall (for the ELISA, on the order of .2% give a false positive; for the Western confirmatory test, false positives occur more like .00001% of the time, with false negatives a bit more commonly at .001% of the time). This is a damn good test, and can additionally be followed up with RT-PCR to determine viral load (even more specific than the protein tests).
As far as differences between countries, I've tried to dig into that, but it's tough to find information out there on that which doesn't come from denialist websites. Different countries may use different confirmatory tests as well, so it's true that there's no universal, worldwide standard as far as HIV diagnosis. In the past, one commenter on my blog has posted standards around the world, and they're not nearly as different as HIV deniers would have you believe. Unfortunately it's tough to search comments and I'm apparently not using the right keyword to find that information right now.
But given that these people live in poverty and may suffer from other conditions, isn't it imperative that testing be done to isolate what exactly is the cause of death or illness?
In an ideal world, absolutely. However, the one thing I agree with the deniers on is that these countries are resource-poor, and there's simply not the funds available to do that for every person. Additionally, in some areas, there are cultural traditions that mean that doing autopsies or any kind of post-mortem work violates their beliefs. It's a tough area to work in, and this is why seroprevalence studies of living individuals are carried out instead--to get a snapshot of viral prevalence and disease in a particular area. It's not perfect, but coupled with some trust in the area physicians (as I mentioned previously) and their familiarity with the disease, it's probably as good as we're going to get for right now. (And in this context, keep in mind the thousands of people here in the US, with all our resources, that also die of undiagnosed causes...)
