Saturday, January 29, 2011

Concurrency: the Favorite Plaything of the Sex-Obsessed HIV Industry

For a relatively short time, the notion of concurrency became the favorite plaything of the sex-obsessed HIV industry. They hypothesized, not just Africans with rampant and uncontrollable sexual urges, but Africans with sexual partnerships that overlapped with each other.

If serial monogamy refers to the practice of finishing one relationship before going on to another, concurrency increases the chances of infecting more than one person. Given normal probability of transmission through penile-vaginal sex, those subscribing to the purely sexual theory of HIV transmission need all the help they can get.

But some have speculated about another aspect of rapid transmission, which has been well demonstrated, but never clearly tied to concurrency. The probability of transmitting HIV is highest during the first three months of infection and during the last 9 months or one year. During the latent phase, which can last 8 years or so, probability of transmission is especially low.

So, if someone acquires HIV, they are highly infectious during the first few months. Sex-only HIV transmission theorists need that person to infect several people during that short period to explain exceptionally high prevalence found in some countries. Concurrency may help explain high prevalence, but it doesn't completely explain it.

More embarrassing for these adherents of the 'behavioral paradigm', the belief that sexual behavior accounts for the bulk of infections, is that concurrency doesn't appear to be very common in many countries, even countries with high HIV prevalence.

People like Jeffrey Eaton, Timothy Hallett and Geoffrey Garnett have gone to great lengths to push concurrency, and the behavioral paradigm in general, but they have even discovered that it just can't be pushed that far. They try to model the effects of relatively low levels of concurrency that also take into account the stage of HIV infection. They even use ridiculously high estimates of transmission rates.

But they are forced to conclude that "this model produces HIV epidemics that grow more slowly than those observed in southern Africa, suggesting that factors not included here—in particular, small groups with greater number of sexual partners and cofactors that increase HIV transmission—also contribute to accelerating the spread of HIV".

This is a completely deflating argument, showing that some level of concurrency has some influence on rates of transmission, possibly. The level of influence, like rates of concurrency, is not estimated. Perhaps it's not even possible to estimate it.

Another study suggests that many people in high prevalence countries don't have very many partners (Table 2). The percentage of people who had more than one partner in the last year before the study ranged from 6% in Malawi to 25% in Lesotho. Fair enough, Lesotho is a high HIV prevalence country, but so is Swaziland, where only 10% had more than one partner.

And having more than one partner is not the same as concurrency. Eaton et al find that "increasing from 10 to 11% of individuals having concurrent partnerships increased the mean endemic HIV prevalence from 3 to 7%." We can't assume concurrency is higher in high prevalence countries without arguing in a circle (though mathematical modeling is probably no stranger to circular arguments). What the researchers say may be true, but we don't know what truth it expresses.

Even if concurrency plays a role and that role can be quantified, how do we then explain the rise, peak and decline in HIV rates in most sub-Saharan African countries before most prevention programs started and long before the notion of concurrency became the popular plaything it is today?

Eaton et al conclude that "primary infection in the context of concurrent sexual partnerships may be the factor that has enabled HIV to spread through general populations to such high levels." They are entitled to conclude that it may be a factor, not the factor. And that doesn't really get us much further.

But there isn't much further to go when your only contribution to HIV transmission theory is that it is a sexually transmitted infection. It is, but to what extent? It is also transmitted from mother to child, by injecting drug use, through unsterile health care practices and even unsafe cosmetic practices.

If Eaton et al want a model that grows like some of the epidemics found in some sub-Saharan African countries, they need to factor in non-sexual transmission. Otherwise they will continue to be in the dark and to leave everyone else in the dark. And the useless HIV prevention strategies that have dominated the field for so many years will continue to fail.



Paddy O'Gorman said...

"Concurrency" became the new lifeboat for HIV orthodoxy a few years back. It took over from dry sex and child rape. All sorts of bizarre, disgusting and improbable sexual practices have been attributed to Africans over the years in order to justify the huge discrepancy between estimates for HIV in Africa compared to the rest of the world.

Dry sex, we were once assured, was the favoured form of sexual intercourse for Africans. The natural lubricant of a woman's body was, we were told, not wanted by African men who, uniquely among humans, preferred sex to be dry. So next time I see an African woman on the street, which is every day here in Dublin, I'm supposed to believe she is likely to have her vagina full of bleach.

Next came child rape. Even a moment's thought (something Aids orthodoxy seems incapable of) would tell you that child rape would be a hugely inefficient way of spreading any venereal disease, but that didn't stop westerners (including us Irish!) telling Africans they really had to learn to stop raping their children.

Then came "concurrency". Apparently, Africans don't copulate more than the rest of the world, just with more partners concurrently. The only thing missing with this theory was any evidence to support it. UNAIDS, in its 2008 annual report, was admirably candid: ”A study in five cities in sub-Saharan Africa found no association between concurrency and HIV prevalence level " and likewise "a small study in Malawi also found no association between the density of sexual networks and HIV prevalence".

So what next? I read about "bride shopping" on this blog site recently. I'm only waiting for that to start turning up on the chat shows as pop stars and the like start telling us how badly behaved African are.

Simon said...

Hi Paddy, thanks for your comments. As you say, there have been many theories, especially ones that required some very prejudiced views to be even vaguely credible.

You're right, even UNAIDS have accepted the lack of evidence for a major role for concurrency. Yet these UNAIDS approved people keep churning out papers about it, this time in the form of a mathematical model, where they seem to be able to use any data that might strengthen their case.

But their case is not strengthened. I just don't understand why the fact that their model doesn't explain the worst epidemics in Africa, yet they don't mention that in the abstract, you have to read the full paper to find that out.

I'm pretty sure they will be plenty more flavors of the month. I just wish they would take a closer look at non-sexually transmitted HIV. But then UNAIDS would have to admit that it has spent years screwing up.