In the case of the CAPS and the NCS, the age of debut for the coloureds was significantly later than that for the blacks but earlier than that for the whites.
For women, the age of sexual debut was significantly lower in the black group than the other groups in all the surveys with two exceptions. For the coloureds in the DHS and the whites in the NCS, sexual debut occurred at a non-significantly later age than the black women P — 0. Sexual experience In both sexes, the proportion of individuals who had experienced sexual intercourse did not differ significantly between the races, with three exceptions.
Firstly in the CAPS, which was the only survey limited to young persons, the proportion who had had sex was significantly higher for the blacks than the other groups.
For men these percentages were The second exception was the significantly lower proportion of Indian women reporting sexual experience.
In only one of the four surveys where this was assessed, did a significantly lower proportion of Indian men report having had sex. Thirdly, in the DHS, a significantly higher percentage of the black women Partner age gap For men, the coloured group had the highest prevalence of partners five or more years older than the respondent. Although absolute numbers were not high, in all three of the 15—49 year old surveys with available data the coloured men had a significantly higher prevalence of older partners than the black men.
In the CAPS there was no association found. Among women, the blacks had the highest prevalence of older partners, excluding the DHS, where the whites had a non-significantly higher prevalence. Number of sex partners For the men in all five surveys, the black group had the highest proportion of individuals who had had more than one sexual partner in the past 12 months. This proportion was significantly higher than all other racial groups in all the surveys.
In the five surveys, the proportion of men with more than one sex partner varied from three- to six-fold higher in the blacks than the other racial groups. The black men also had a higher mean number of sexual partners in the past 12 months than the other groups. The mean for the coloured men was significantly lower than that of the black men in the NCS and non-significantly lower in the other surveys.
In all the surveys the mean for the coloured men was intermediate between that of the black and white men. In the case of the women, there was little evidence of a covariance between racial HIV prevalence and number of sexual partners. In all five surveys with data, the Indian women had a significantly lower proportion with more than one partner than the black women. The CAPS was the only survey with data on the lifetime number of sexual partners.
There was no evidence of a variation between race and this variable in this survey. In blacks, coloureds and whites, the mean number of lifetime partners in this survey of young persons was 2. Concurrency In the case of the men, the black group had higher self-reported concurrency prevalences than the other groups in all five surveys. The concurrency prevalence in the black group varied from 7 to 16 times higher than that of the whites in the different surveys.
In all the surveys the coloured men had an intermediate prevalence of concurrency between that of the whites and blacks. In the case of the women, self-reported concurrency prevalences were highest in the black group in all five surveys with available data, but this relationship was only statistically significant in the CAPS. In the CAPS, the cumulative concurrency prevalence in the black women In the DHS, concurrency in those who were married was higher in the blacks 7.
Condom usage Condom use at last sex was most prevalent amongst the black group for both men and women. The only exceptions to this were the women in CAPS and the men in the DHS where the white groups had non-significantly higher condom usage rates than the black groups. Circumcision The prevalence of self-reported circumcision was highest amongst the black group in all three surveys that collected data on this.
Typically prevalences were more than twice as high amongst the blacks than the other racial groups. The large differences in HIV prevalence between the various races in South Africa offer a useful standpoint from which to investigate putative risk factors. South Africa has conducted three nationally representative HIV serosurveys that include 15—49 years olds. In , the HIV prevalence in 15—49 year olds was HIV prevalences by race vary to a similar degree in the other two surveys conducted in  and  as well as in a nationally representative sample of 15—24 year olds  , a national survey of tertiary students  , a survey of company employees  and the country's annual antenatal surveys .
Controlling for various socioeconomic variables makes little or no difference to the differences in HIV prevalence by race  ,  , . An example is provided by a multivariate analysis of the HIV survey. When education and socioeconomic status are controlled for, being black remains the strongest factor associated with testing HIV positive — the odds ratios varying from 7. There has only been one published study that has attempted to systematically explore the risk factors which co-vary with HIV prevalence by race in South Africa .
This study found that the individual-level risk factors such as number of sex partners in the last 12 months, condom usage and circumcision prevalence did not co-vary with HIV prevalence by race. The prevalences of partner and respondent concurrency, both network-level properties, were however found to differ considerably between the different racial groups and to do so in a way which mirrored the differences in HIV prevalence.
This study was limited to 14—22 year olds in the city of Cape Town. The current study extends this analysis to include five nationally representative samples of 15—49 year olds. Its findings concur to some extent with the Cape Town study. The Indian and white groups are both numerically small and have similarly low HIV prevalences.
If we consider them together as the low HIV prevalence groups, then the risk factors which co-vary with HIV prevalence by race in the six surveys are age of sexual debut in five out of five surveys for men and three out of six surveys for women , age gap zero surveys in men and three in women , mean number of sex partners in the previous year five surveys in men and one in women and respondent concurrency five surveys in men and one in women. Condom usage and circumcision were both more prevalent in the high HIV prevalence groups.
There was little evidence of difference in the prevalence of those who had had sex. The survey which demonstrated the largest difference in this variable was the CAPS. This was likely due to the fact that it was the only survey which was limited to younger persons. In four of the five surveys where people up to the age of 49 were included, there were no differences in sexual experience.
Which of the co-varying risk factors could be responsible for the large differential HIV spread by race? Age of sexual debut, by itself, is an unlikely candidate. This is for a number of reasons, including the fact that the age of sexual debut in the highest HIV prevalence groups is higher than that in the very low prevalence countries of the USA  and Western Europe .
A number of publications have argued that age-mixing plays a significant role in HIV spread in sub-Saharan Africa  ,  , . Age-mixing, whilst of likely importance, cannot without an interconnected sexual network result in a generalized HIV epidemic.
This is evident if we consider a hypothetical population where there is an age gap of 10 years in all couples but the couples practice exclusive lifetime monogamy. Purely sexually transmitted infections cannot spread in this population despite extreme age-mixing since STI spread depends on an interconnected sexual network .
Factors such as age-mixing are, however, likely to influence transmission across an interconnected network, particularly to new cohorts of younger persons  , . The fact that, in three out of five surveys of women, the prevalence of age-discordant coupling co-varied with HIV prevalence may be indicative of age-mixing having an influence on HIV prevalence.
This analysis finds evidence of a covariance between concurrency and HIV prevalence. Higher prevalences of sexual partner concurrency have been shown to lead to exponential increases in the degree of network connectivity and thereby the potential for HIV transmission . Although certain studies have not found an association between HIV and concurrency  ,  , a number of good modeling-based and empirical studies have shown that concurrency prevalence covaries closely with HIV prevalence inter- and intra-nationally  ,  ,  ,  and that it is a key driver of incident HIV at a partnership level in sub-Saharan Africa .
In particular declines in concurrency have been shown to be important in the rapid decline of HIV incidence in Zimbabwe, Uganda and elsewhere  , . Amongst the women, the prevalence of concurrency was only higher in the blacks in one of five surveys — the CAPS survey. Finding lower prevalence of concurrency in women compared to men is a common result of surveys in Southern Africa and further afield  ,  ,  ,  ,  ,  , . This may reflect a combination of a lower prevalence of concurrency  and a differential male-female courtesy bias induced by the fact that concurrent partnering is considerably more stigmatized for women than men in many communities .
The importance of a courtesy bias in this regard is suggested by studies in Southern Africa that found that changes in the ways that surveys are conducted and the ways questions are asked, can lead to a significant increase in the measured prevalence of concurrency in women  , . Even in the likely scenario that women are less likely to have concurrent partners than men, concurrency can still lead to extensive HIV spread in women. This is for two main reasons.
Firstly, at an individual level, concurrency acts to increase the risk of HIV to the partners of the individual engaging in concurrency rather than to the individual him or herself  ,  , . Secondly, and most importantly, concurrency's major impact on HIV transmission operates by connecting together a large proportion of the population into a transmission pathway for HIV  , . This is a network level effect and thus would be experienced by all members of the connected-network both men and women.
The total number of sexual partners, though important, is less likely to be a crucial factor for a number of reasons. Secondly, the available evidence suggests that much of the higher number of sexual partners in the past year amongst the black group represents long-term concurrent partnering  , .
This is supported by the fact that this analysis could find no evidence of a difference in the total life-time number of partners between the races. Other comparative studies of sexual behavior in sub-Saharan Africa have reached different conclusions. Only age-mixing was more prevalent among South African women. Of note, this study did not assess differences in concurrency prevalence .
Limitations There are a number of limitations that apply to this study. The surveys used were based on interviews about sensitive topics which were generally conducted in the respondents' residences, often with other individuals within listening distance. In addition some of the surveys had low response rates. The data is thus susceptible to a large number of biases such as courtesy, recall and non-response biases. There is however little evidence that we are aware of that there is a difference in sexual behaviour between those who do and do not answer sexual behavior questionnaires .
This is important as there was evidence of a differential response rate by race in some of the surveys. If responders varied from non-responders by sexual behavior then this could confound our results. It is likely that sensitive information such as the extent and type of multiple-partnering is underreported, particularly among women . There was however no evidence we could find of a differential bias by racial, ethnic or national group in this or any other sexual behavior topic.
Since the comparisons were between racial groups within each survey, this type of underreporting should not invalidate our comparisons. Differences in current HIV prevalence therefore reflect the cumulative effect of behaviours over the preceding years.
Behaviors may have changed over this time and they may have changed in response to the HIV epidemic. The surveys reviewed here, do however, span a period from — and there is little evidence of a change in the variance of the risk factors by race over this period.
As an example the only longitudinal study that we are aware of that has reported changes in the prevalence of concurrency in South Africa has found that the difference in concurrency prevalence between black and coloureds has not changed between the times it was measured — . The clearest example of a change is the increase in condom usage, which is likely a response to the HIV epidemic . If we compare condom use at last sex between the earliest survey DHS and the last survey NCS , condom usage has increased in all groups.
The initial prevalence of condom usage in the black women no men were surveyed in was however higher