The spread of HIV through populations around the world was remarkably uneven. Of the 149 countries for which the WHO provides data, 98 had a peak HIV prevalence that never went above 1% and only in 20 countries peak HIV prevalence exceeded 5% [
There is still considerable debate about what determines these differences. A number of studies investigating this issue have utilized individual level risk factor study designs [
Secondly, we assess if ethnic groups more heavily affected by HIV have higher rates of other STIs preceding the HIV epidemic. The answer to this question has significant consequences. If there was no correlation between HIV and STI prevalence then the affected populations likely suffer from some factor that makes them specifically more vulnerable to HIV. This would give more credence to HIV prevention strategies that focused on HIV specific responses such as antiretroviral treatment as prevention [
All the data used were taken from published studies. The individual studies providing this data are described in Table
Description of sources of data for prevalence of STIs, multiple partners, concurrency, and circumcision.
Year in which data were collected, reference | Study type, selection procedure, sample size, response rate, and testing protocol for syphilis | |
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HIV | 2005 [ |
A two-stage, nationally representative sample of 23,275 persons 2 years old or older. We limited our analysis to the 13,884 individuals aged 15 to 49 years old. The survey had an overall response rate of 80.7% |
HSV-2 | 2012 [ |
A sample of 18,732, 15–49-year-old women attending antenatal clinics for the first time in four provinces (Western Cape, Northern Cape, Gauteng, and Kwazulu Natal) were tested for HSV-2. Response rate not reported |
Syphilis | 1991 [ |
A sample of 17,318, 15–49-year-old women attending antenatal clinics for their first visit were tested for syphilis via the Rapid Plasma Reagin or the Venereal Diseases Research Laboratory test. Response rate not reported. The unadjusted prevalence estimates were used |
Urethral discharge | 1998 [ |
South Africa’s first Demographic and Health Survey employed a 2-stage sampling strategy in South Africa’s nine provinces and stratified results into urban and nonurban groups. It was designed to be representative of all provinces and the four major racial groups. 6,578 men were asked if they had experienced symptoms of a urethral discharge in the last 3 months. The overall response rate for men was 89.7%. Men were not asked questions about their sexual behavior in this survey |
Concurrency, multiple partners, |
2003 [ |
The 2003 Demographic Health Survey (DHS) used a similar study design to the 1998 DHS. The survey sampled 7,966 women and 3,930 men. All were 15–49 years old [ |
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HIV | 2006 [ |
HIV prevalence at the end of 2006 was estimated using information from the national HIV/AIDS reporting system |
HSV-2 | 1988–94 [ |
In NHANES III, a national stratified probability sample of 13,094 individuals over the age of 12 were tested for HSV-2. These persons comprised 60.5% of all respondents in NHANES III |
2005–09 [ |
During NHANES 2005–2008, a total of 8,283 persons aged 14–49 years were interviewed. Of these, 7,293 participants (88% of those interviewed) were tested for HSV-2 antibodies | |
Syphilis | 1976–80 [ |
In NHANES II a national stratified probability sample of 12,989 individuals over the age of 12 were tested for syphilis. 92% of those who were examined provided blood for syphilis testing. The initial test was with an RPR and confirmation with a microhemagglutination assay for |
2001–2004 [ |
Sera from 5,767, 18- to 49-year-old participants in the NHANES 2001–2004, were tested for syphilis IgG antibody using an enzyme immunoassay (EIA). Specimens with positive or indeterminate EIAs underwent rapid plasma | |
Concurrency and multiple partners | 1992 [ |
The USA |
Circumcision | 1999–2004 [ |
As part of National Health and Nutrition Examination Surveys from 1999 to 2004, 6,174 men were interviewed about circumcision status. The response rate was 86% |
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HIV, MUDS, and circumcision | 2008 [ |
The 2008 Kenya Demographic and Health Survey used a household-based, two-stage stratified sampling approach to recruit 12,677 participants. The overall household response rate was 97.7% |
HSV-2 and syphilis | 2007 [ |
The 2007 Kenya AIDS Indicator Survey used a stratified two-stage sampling strategy to test a nationally and provincially representative sample of 15,853, 15–64-year olds. Syphilis was screened for via a |
Concurrency and multiple partners | 2011 [ |
The Population Services International (PSI) Survey/Kenya 6th HIV Survey conducted in 2011 used a two-stage cluster sampling to obtain a provincially representative sample of households from seven of Kenya’s eight provinces (the North East was excluded). A total of 3,051 men and women, 15–49 years old, were included. Response rate not reported |
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HIV and MUDS | 2010–2012 [ |
National Surveys of Sexual Attitudes and Lifestyles 3 recruited a probability sample of 15,162 women and men aged 16–74 years in Britain. Participants were interviewed with computer-assisted face-to-face and self-completion questionnaires. Urine from a sample of participants aged 16–44 years who reported at least one sexual partner over the lifetime was tested for HIV antibodies |
Concurrency, multiple partners, STI, and circumcision | 2000 [ |
The second British National Survey of Sexual Attitudes and Lifestyles (NATSAL 2) was a nationally representative sample of 11,161 men and women aged 16–44 years [ |
DHS: Demographic and Health Survey, NATSAL: National Survey of Sexual Attitudes and Lifestyles, NHANES: National Health and Nutrition Examination Surveys.
The prevalence of
The prevalence of
The prevalence of
The prevalence of
All
In the case of the UK and USA the proportion reporting MUDS was not available. For the UK and USA we used the proportion of men who reported having ever before been diagnosed with an STI (UK) or gonorrhoea (USA).
All the variables were limited to the 15–49-year-old age group except the circumcision and sexual behavioural data from the USA which was reported in 18–59-year olds; the HSV-2 data from the USA in 1976–1980 and 1988–1994 which included all those who aged 12 years or older; the sexual behavior data from the UK referring to 16–44-year olds; HSV-2 and syphilis prevalence in Kenya referring to 15–64-year olds.
The small number of ethnic/racial groups per country makes the use of statistical tests of correlation of questionable merit. Nonetheless we investigated the statistical significance of the correlations between HIV and the other STIs and risk factors using Spearman’s correlation coefficient. We chose Spearman’s correlation coefficient for these analyses as the sample sizes were small and in a number of cases the relationship between the variables was nonlinear. The analysis was performed using STATA 12 software (Stata, East College Station, TX, USA). Where appropriate, the SVY function was used to adjust for complex survey designs and differential nonresponse rates. Because of the small number of ethnic/racial groups per country, a
The relative risk of HIV by ethnic/racial group varied between 7.8 and 39.8 within each country (for prevalences of each STI see Table
The prevalence of HIV, syphilis, HSV-2, STI symptoms, concurrency, multiple partners, and circumcision by ethnic/racial group.
Country | Ethnic/racial group | HIV | Syphilis (early)a | Syphilis (late)b | HSV-2 (early)c | HSV-2 (late)d | STI symptoms | Concurrency | Multiple partners | Circumcision |
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USA | Non-Hispanic white | 0.22 (0.21–0.24) | 0.53 (0.39–0.67) | 0.07 (0.01–0.28) | 17.6 (15.7–19.8) | 12.3 (10.7–14.2) | 5.8 (4.6–7.3) | 3.1 (2.2–4.3) | 15.0 (14.0–16.5) | 88e |
Hispanic | 0.59 (0.53–0.64) | 0.98 (0.49–1.74) | 22.3 (21.2–23.5) | 10.1 (8.3–12.) | 8.7 (2.7–17.8) | 8.9 (3.6–19.9) | 19.9 (15.7–24.7) | |||
Non-Hispanic black | 1.72 (1.61–1.82) | 3.05 (2.18–3.92) | 4.3 (3.23–5.53) | 45.9 (43.9–47.9) | 39.2 (36.7–41.7) | 32.2 (25.9–39.0) | 11.3 (7.5–16.7) | 27.1 (23.8–31.4) | 73e | |
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SA | White | 0.5 (0.3–1.1) | 0.4 (0.1–0.9) | 19.5 (12.7–28.2) | 2.0 (0.7–3.2) | 2.0 (0.3–12.5) | 4.9 (2.1–11.2) | 21.7 (13.8–32.5) | ||
Coloured | 3.2 (2.3–4.6) | 6.3 (5.4–7.3) | 30.3 (28.1–32.5) | 5.9 (4.2–7.5) | 6.5 (2.7–14.8) | 8.2 (4.9–13.6) | 15.9 (10.6–23.0) | |||
Black | 19.9 (18.3–21.7) | 8.3 (7.8–8.8) | 60.8 (60.1–61.5) | 13.2 (12.2–14.2) | 9.2 (7.1–12.0) | 16 (13.9–18.3) | 50.2 (47.3–53.7) | |||
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Kenya | Nairobi | 7.2 (4.2–12.2) | 1.4 (0.8–2.1) | 34.7 (32.3–37.3) | 0.91 (0.23–3.5) | 16.0 (11.7–20.8) | 25.8 (19.8–32.9) | 89.5 (81.1–94.4) | ||
Central | 4.6 (3.2–6.8) | 1.2 (0.7–1.8) | 43.8 (41.1–46.5) | 0.88 (0.22–3.3) | 14.5 (11.1–18.4) | 24.4 (17.3–33.3) | 97.0 (94.1–98.5) | |||
Coast | 4.2 (2.6–7.0) | 1.8 (1.1–2.7) | 61.8 (58.9–64.6) | 0.18 (0.04–0.77) | 11.7 (8.5–15.6) | 19.9 (14.2–27.3) | 96.7 (92.7–98.6) | |||
Eastern | 3.5 (2.1–5.5) | 2.2 (1.5–3.1) | 39.9 (37.3–42.5) | 0.24 (0.05–1.0) | 6.4 (4.2–9.2) | 12.2 (7.4–19.5) | 96.8 (93.6–98.4) | |||
Nyanza | 13.9 (11.0–17.9) | 2.5 (1.8–3.4) | 76.2 (73.9–78.3) | 3.45 (2.0–5.8) | 18.2 (14.9–21–9) | 30.6 (23.8–38.3) | 44.3 (32.6–56.8) | |||
Rift Valley | 4.7 (3.1–7.3) | 1.8 (1.2–2.6) | 52.6 (50.1–55.1) | 0.54 (0.2–1.6) | 10.3 (7.6–13.5) | 14.4 (10.5–19.4) | 91.1 (86.3–94.3) | |||
Western | 6.6 (4.9–9.2) | 1.0 (0.5–1.7) | 59.9 (57.0–62.6) | 1.52 (0.7–3.2) | 18.8 (14.0–24.3) | 20.9 (18.4–23.7) | 93.7 (88.5–96.6) | |||
North Eastern | 0.9 (0.3–4.0) | 0.5 (0.2–1.4) | 15.6 (12.9–18.5) | 0 (0-0) | — | — | 98.7 (96.1–99.6) | |||
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UK | White | 0e | 10.9 (9.9–12.0) | 13.9 (12.7–15.3) | 29.6 (28.1–31.1) | |||||
Black Caribbean | 2.8 | 19.7 (13.6–27.9) | 25.4 (17.6–35.1) | 41.6 (31.3–52.7) | ||||||
Black African | 2.8 | 16.2 (10.8–23.4) | 34.5 (22.8–48.3) | 43.8 (34.1–54.1) | ||||||
Indian | 0 | 3.4 (1.0–11.9) | 16.1 (8.0–29.8) | 23.2 (16.5–31.5) | ||||||
Pakistani | 0 | 3.2 (1.3–7.5) | 13.2 (6.9–23.7) | 22.7 (14.8–33.2) |
bUSA data from 2001–2004 [
cUSA data from 1988–1994 [
dUSA data from 2005 to 2009 [
eConfidence intervals were not specified.
The prevalence of HSV-2, syphilis, and symptomatic STI versus HIV prevalence by ethnic group in Kenya, South Africa, the United Kingdom, and the United States of America.
The prevalence of concurrency, multiple partnering, and circumcision versus HIV prevalence by ethnic group in Kenya, South Africa, the United Kingdom, and the United States of America.
All three STI categories were positively associated with HIV prevalence in all countries (see Table
Spearman’s correlation coefficient (rho) for the relationship between HIV prevalence and various risk factors and other STIs by racial/ethnic group in Kenya, South Africa, the United Kingdom (UK), and the United States of America (USA).
Kenya | South Africa | UK | USA | |||||
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Spearman’s coefficient |
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Spearman’s coefficient |
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Spearman’s coefficient |
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Spearman’s coefficient |
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HSV-2 (early) | 1.0 | 0.000 | ||||||
HSV-2 (late) | 0.50 | 0.207 | 1.0 | 0.000 | 0.50 | 0.667 | ||
Syphilis | 0.33 | 0.420 | 1.0 | 0.000 | 1.0 | 0.000 | ||
STI symptoms | 0.92 | 0.001 | 1.0 | 0.000 | 0.87 | 0.058 | 1.0 | 0.000 |
Concurrency | 0.786 | 0.036 | 1.0 | 0.000 | 0.87 | 0.058 | 1.0 | 0.000 |
Multiple partners | 0.821 | 0.023 | 1.0 | 0.000 | 0.87 | 0.058 | 1.0 | 0.000 |
Circumcision | −0.05 | 0.215 | 0.5 | 0.667 | −0.50 | 0.667 |
Although the relationship between HIV and syphilis rates was positive in the three countries assessed, this relationship was only statistically significant in South Africa and the USA (Spearman’s correlation coefficient = 1.0;
There were large variations in the prevalence of circumcision, multiple partnering, and concurrency by ethnic group. The prevalence of circumcision by ethnic group in USA, SA, and Kenya varied by a factor of up to 1.2, 3.2, and 2.2, respectively. The prevalence of multiple partnering in the USA, SA, Kenya, and the UK varied by a factor of up to 1.8, 3.3, 2.5, and 1.9, respectively. Concurrency prevalence in the same countries varied by a factor of 3.6, 4.6, 2.9, and 2.6, respectively.
There was no statistically significant correlation between circumcision and HIV prevalence in any of Kenya, SA, or USA. The prevalence of circumcision by race in the NATSAL surveys from the UK was not reported but it was stated in the report that, “with the exception of black Caribbeans, men from all ethnic minority backgrounds were significantly more likely to report being circumcised compared to men who described their ethnicity as white (adjusting for various demographic variables) (adjusted odds ratio (OR) 3.02, 95% CI 2.39 to 3.81)” [
The prevalence of multiple partnering and concurrency were positively associated with HIV prevalence in all countries. This association was statistically significant in all cases (Spearman’s correlation coefficient ranging from 0.79 and 1.0).
In all four countries HIV prevalence was positively correlated with the prevalence of HSV-2, syphilis, and males reporting an STI. This positive association applied to the pre-HIV and HIV periods. In the case of HSV-2 in the USA, there was little change in the relative differences in HSV-2 prevalence between the various racial/ethnic groups over a 32-year period. Thus HSV-2 prevalence in non-Hispanic black women was as high in 1976 (51%) as in 2008 (48%). Studies that control differences such as age structures between the different surveys have found that there has been a small increase in the non-Hispanic black to white ratio of syphilis over this time period [
In SA the earliest comparison of HSV-2 prevalence by racial group was a survey of blood bank donors in 2005 [
A strong association between HIV and HSV-2 has also been found at the level of countries and world regions. A study of 52 countries found a strong correlation between peak HIV and HSV-2 prevalence in 40–44-year-old women (Spearman’s correlation coefficient = 0.720;
We also found associations between HIV and syphilis and HIV and males reporting STIs. Similar associations have been found at the country and world region levels between the prevalence of syphilis before the HIV epidemic and peak HIV prevalence [
Four factors suggest that the association between HIV and other STIs is due to factors which act as general STI transmission enhancing factors. Firstly, the association between HIV and other STIs has been found at different levels of aggregation (by ethnic group within countries, cross country, and between world regions) [
We examined three possible risk factors. Various pieces of evidence, including those presented here, suggest that differences in circumcision rates play a role in determining the more extensive HIV epidemic in the Luo in Nyanza Province in Kenya, than other groups [
Although this study only includes four countries both multiple partnering and concurrency were positively associated with HIV prevalence in all countries. Little more can be concluded from this other than this finding is congruent with findings elsewhere that populations with higher rates of partner change and concurrency have a higher prevalence of HIV and other STIs [
There are however a number of serious limitations to this study. Only three risk factors are investigated which means that our results could represent confounding. A variety of socioeconomic factors have been shown to be important in the genesis of differential STI rates by race/ethnic group in the USA [
The prevalence of an STI in a particular community represents the composite outcome of the interaction of a number of different risk factors [
The authors declare that there is no conflict of interests regarding the publication of this paper.