Writes Key Correspondent, Henry Neondo.
According to a study by two US researchers, promoters of the concurrency hypothesis have failed to establish that it is unusually prevalent in Africa or that the kinds of concurrent partnerships found in Africa produce a more rapid spread of HIV than other forms of sexual behaviour.
Larry Sawers, of American University, and Eileen Stillwaggon, of Gettysburg College, say quantitative evidence cited by proponents of the concurrency hypothesis excludes demographic and health surveys and other data showing that concurrency in Africa is low.
Prevalence of HIV in some countries of sub-Saharan Africa is up to 50 times higher than the average for countries outside Africa.
In the 1990s, it was widely accepted in policy and scholarly discourse that higher rates of risky sexual behaviour in Africa explained the difference in HIV prevalence.
That conventional wisdom was repeated in hundreds of articles, books and policy documents, as well as in popular media. Careful examination of empirical evidence, however, compelled social scientists and policy makers alike to acknowledge that most kinds of risky sexual behaviours are not exceptionally common in sub-Saharan Africa.
On the contrary, the researchers say the rates of risky behaviours are considerably higher in affluent and middle-income countries with low HIV prevalence, including early initiation of sex, number of sexual partners, and premarital and extramarital sexual relations.
Confronted with that evidence, defenders of the notion that some form of risky sexual behaviour must explain the high HIV prevalence in sub-Saharan Africa narrowed their argument to a single kind of sexual behaviour: concurrency, which they define as long-term, overlapping partnerships.
The concurrency hypothesis, say the study, consists of two claims: that concurrency leads to more rapid spread of HIV than other forms of heterosexual partnering and that concurrency is more prevalent in eastern and southern Africa than in the rest of the world.
But they concede that whether concurrency is much higher in Africa than elsewhere and, consequently, whether it is the appropriate focus of HIV-prevention policy remains in contention.
However, the researchers say given that all of the studies that have looked for a statistical correlation between concurrency and HIV either have important limitations (Likoma) or find no correlation (all the rest), the proponents of the concurrency hypothesis have had to turn to other evidence to make their case.
First, they argue that mathematical modelling shows that HIV can spread far more rapidly if long-term, overlapping partnerships are common compared with situations where multiple partnering is confined to serial monogamy.
Second, they offer quantitative evidence that they claim shows a higher level of concurrency in sub-Saharan Africa than elsewhere. Last, they present qualitative evidence about attitudes, perceptions and beliefs to support their argument.
But evaluating each argument and each datum, we find that the “totality of the evidence” does not support the hypothesis. According to the study, errors they encountered from the proponents of concurrency are the assumptions that everyone in a partnership has sexual contact with every one of their partners every day.
“Most people do not have sex every day with multiple partners”, they said adding that no one can justify daily sex assumptions.
The researchers say empirical evidence from 13 studies show far lower frequency of sexual contact in Africa than previously assumed.
For example, a study of South African sexually experienced men and women aged 15-24 years who that 90% or more reported having had sex fewer than five times in the previous month.
In Lesotho, Tanzania, Togo, Burundi and Cote d’Ivoire, between 32% and 59% of adults with regular partners reported no sex with their regular partner in the previous month.
In those countries, say the two researchers, mean coital frequency with regular partners in the previous month was 4.0 for adult men and 3.2 for adult women.
Data from the Demographic and Health Surveys (DHS) for nine sub-Saharan African countries shows that the frequency of sex among women in their first year of marriage ranged from two times a month in Mali and Burkina Faso to 4.4 times per month in Malawi and averaged 3.2 times per month. Coital frequency in later years of marriage was much lower.
The two also dispute equal concurrency between male and female. They dispute arguments that ‘as soon as one person in a network of concurrent relationships contracts HIV, everyone else in the network is placed at risk. By contrast, serial monogamy traps the virus within a single relationship for months or years’.
Nevertheless, if women do not have concurrent partners, then HIV infection is “trapped” in the same way that it is with serial monogamy, blocking the formation of “extensive interlocking sexual networks”.
The two dispute assumptions of per-act transmission rate of 0.05. they say this is too high.
They say a study in Rakai the level of concurrency found in Rakai and the generally accepted transmission rate of 0.001, every adult in Rakai would have to have 47 sex acts per day per partner to reproduce Morris and Kretzschmar’s results.
They argue that after the first few weeks of acute infection, the transmission rate drops to levels far below the rate used previously.
Numerous studies have found that between heterosexuals who are otherwise healthy, the per-act transmission rate during asymptomatic infection (after the brief acute infection period) is about one in 1000 contacts.
Even that transmission rate may be an overestimate since some studies did not control for such factors as blood exposures, cofactor infections or anal intercourse.
During acute infection, no one has found a heterosexual transmission rate as high as 0.05 in the absence of cofactor infection.
The researchers say sexual behaviour alone simply cannot explain the extraordinarily high HIV prevalence in much of Africa.
They however suggest two possible explanations for Africa’s extraordinary HIV epidemics. First, they say, the per-act heterosexual transmission of HIV between otherwise healthy adults, even during acute infection, is very low, but many bacterial, viral and parasitic infections can make infected partners more infectious and uninfected partners more vulnerable over extended periods by raising transmission rates.
The role of sexually transmitted infections, STIs in promoting HIV transmission has been widely discussed.
For example, after finding a strong association between HIV and HSV-2 in the four-city data, studies say that the “differences in efficiency of HIV transmission as mediated by biological factors outweigh differences in sexual behaviour in explaining the variation in rate of spread of HIV between the four cities”.
Additionally, urogenital schistosomiasis (Schistosomiasis hematobium), found mostly in Africa, produces urogenital lesions in women and men, increases viral shedding of the infected partner, and produces genital inflammation for the uninfected partner, all of which facilitate transmission of HIV.
Women with genital lesions of schistosomiasis were three times as likely to contract HIV as women in the same Zimbabwean villages who did not have those lesions.
Malaria also raises viral load, making the infected partner more contagious.
The burden of those and other diseases suspected of increasing HIV transmission is far higher in sub-Saharan Africa than elsewhere.
The second explanation for the African HIV epidemics that merits further attention is blood exposures, such as unsterilized syringes, other invasive medical and dental procedures, circumcision (either in a medical setting or elsewhere), treatment by informal injection, tattooing, sharing of hairdressing equipment, therapeutic bloodletting and so on.
Many forms of blood exposure are far more efficient at transmitting HIV than most heterosexual behaviours.
Even WHO admits that 30% of injections in eastern and southern Africa use unsterilized needles and 10% of new HIV infections worldwide come from unsterile injections and blood transfusions.
The two call for an end to research on sexual behaviour in Africa of this kind and say it is no longer justifiable to continue to waste financial and human resources to prove Western preconceptions about African sexuality cannot be justified.