There are an estimated 33 million people living with the HI virus worldwide. Of these, twothirds live in countries south of the Sub-Saharan Africa. In addition, out of the estimated 2.5 million new infections occurring globally, two thirds are also in sub-Saharan Africa (UNAIDS, 2007).
It is estimated that South Africa is one of the countries with the largest number of HIV infections in the world. In 2008, UNAIDS estimated that there were 5.3 million 4.
5.7 million people living with HIV. The HIV prevalence data collected from the latest round of antenatal clinic surveillance suggests that HIV infection levels among the adult female population might be leveling off, with prevalences among pregnant women at 29.1% in 2006 and 29.4% in 2007.
It is for this reason, that the Department of Health (DoH) strategic focus to strengthen HIV prevention and AIDS related disease management and control remains one of the priorities of the South African government. The country has adopted a multi-sectoral strategic approach in dealing with the spread of HIV and mitigating the impact of AIDS related morbidity and mortality. This approach ensures that all relevant stakeholders play an active role in combating HIV and AIDS in their areas of comparative advantage, with the DoH providing a lead role.
The general objective of the 2008 National HIV and Syphilis Prevalence Survey is to monitor the epidemic and provide HIV prevalence data for planning, monitoring and evaluation of HIV and AIDS response activities.
To determine the National HIV and syphilis prevalence among the female population of 15 -49 years in the country using pregnant women attending antenatal clinics in public health institutions as proxy.
To determine the distribution of HIV and syphilis infection among pregnant women attending antenatal clinics by province, district and age.
To monitor the trend of HIV and syphilis infection in the country over time.
To project and extrapolate HIV prevalence in the 15 -49 year old female to the general population e.g. children, men and those who need treatment.
To make information available for policy-planning, focused strategic programmes, advocacy, and evaluation of impact of ongoing interventions.
This report presents the results of the 2008 National Antenatal Sentinel HIV and Syphilis Prevalence Survey and trends in HIV and syphilis over the years. The results will provide a basis for the projection, estimation of the epidemic and measurement of HIV and AIDS impact in the general population.
The 19th National Antenatal HIV and Syphilis Prevalence Survey was conducted in all the nine provinces of the country using the standard unlinked and anonymous methodology (WHO/UNAIDS) in October 2008. The survey is used as a proxy to estimate the trend in the prevalence of HIV and syphilis among pregnant first bookers aged 15 -49 years served in public health facilities. A total of 33 927 pregnant women participated in 2008 compared to 33 685 in 2007. The women were recruited from 1 457 sentinel sites.
The South African annual antenatal HIV surveillance survey is an anonymous, unlinked, cross-sectional survey targeting 15 -49 year old pregnant women attending antenatal clinics in the public health sector. Only first-time attendees were recruited, to minimize the chances of any woman being included more than once. Since 2006, this survey has expanded its sample population to target 36 000 pregnant women from 1 457 clinics compared to 16 510 women recruited from 339 clinics in 2005 (see Figure 1). This has expanded geographic coverage considerably to include representativity in all 52 health districts in all the nine provinces.
The protocol and methodology were reviewed with all provincial survey coordinators. In addition, pre-2008 survey workshops were held at the National Department of Health as well as in all nine Provincial Health offices before the scheduled commencement date of the survey. Participants in these workshops included provincial and laboratory coordinators, health information officers, data capturers, and facility nurses. The training covered criteria for selection of the sites, recruitment of pregnant women, data administration, blood sample collection, labelling, coding, storage of samples, sample transportation, syphilis and HIV testing, confidentiality and ethical issues, supervision and quality assurance procedures.
This study was conducted as an unlinked anonymous survey amongst pregnant women who attended public health antenatal clinic services for the first time during the current pregnancy. The demographic details of the participants, with the exception of any particulars from which it may be possible to ascertain the identity of a patient, were collected using a standardized collection form. A unique bar code was allocated to each of the participants and it is this number that was recorded on the form and also used for labelling the blood samples. The bar code was used to link the demographic information with the lab results while maintaining anonymity of the survey participant.
The selection of sites was based on the geographical distribution taking into account all the nine provinces and 52 districts of the country, presence of antenatal care services, existence of facilities for storing of blood specimens, availability of transport to allow for samples to be taken to the laboratory, the ability and willingness of antenatal care providers to cooperate and participate in the survey. The geographical location of the sentinel sites is shown in Figure1.
Overall a proportional sample by district was drawn using the first time antenatal clinic attendees as obtained from the District Health Information System (DHIS) as a measure of size. This allowed for establishing the plausibility of the number of proposed samples to be collected at facility level.
The selection of eligible sentinel sites within a district was based on the Probability Proportional to Size (PPS) sampling method. Since the sampling period in each facility was the same this produced a self-weighting sample for each district.
A total of 36 000 pregnant women were target in this survey. In order to obtain an estimate of the point prevalence and to assess trends over time, sample collection from all the sites started on 1st October 2008 and ended on 31st October 2008.
Participation in the survey was voluntary, with informed consent for answering the questions on the forms and for collecting the blood samples. For reasons of confidentiality, testing was done on anonymous unlinked samples, in large batches. Syphilis screening is routinely done in the ANC clinics. Hence, syphilis screening was used as an entry point for HIV testing using anonymous unlinked procedures. One blood sample was taken by venous puncture and stored at 4ºC. The corresponding data collection form (Appendix A) with the woman's demographic details was labelled with the same bar code number. At the close of each day the supervisors checked the forms against the blood samples for any mistakes and for completeness. The samples, together with the forms, were transported in a cooler box to the participating provincial laboratory where HIV and syphilis testing was done.
Several measures were put in place to ensure that the results were valid and reliable. Internal quality control for ELISA and RPR tests was the responsibility of each individual participating laboratory. The National Institute for Communicable Diseases (NICD) and the Medical University of Southern Africa (MEDUNSA) served as external quality control institutions for HIV and syphilis respectively.
Raw data was captured at provincial level, using Microsoft Excel. Data cleaning was done by running all frequencies, identifying missing and duplicate records, entering missing records, deleting duplicate records and filling in missing data. Records, for which the age, facility and district name was not available, were removed from the dataset that was to be analyzed. Records, which did not have a confirmed HIV result, were also removed from the database and thus not analyzed. In this survey, 127 out of 33 927 samples were excluded from the analysis because of missing data. STATA statistical software package was used for validation and survey analysis. The analysis was mainly descriptive and focused on determining national, provincial, district and age group specific prevalence rates of HIV and syphilis. 95% confidence intervals were estimated for all the prevalence estimates and these estimates were adjusted for the complex survey design.
The national estimate was weighted using the same weighting procedure as previous years, i.e. according to the total number of women aged 15 -49 years in the different provinces using the STATSSA mid-year population estimates for 2008. Given that the sentinel sites were chosen on a probability proportional to size basis by district, the sampling period was fixed and the districts are self-weighting, the provincial prevalence estimates were simply calculated as the total of the results from the districts in the provinces.
For the 95% confidence intervals, the normal approximation to the binomial distribution was used. In a few cases where the sample size or prevalence was small, the exact binomial calculation was used.
HIV status - either positive or negative by splitting the original sample at an estimated cut point of the variable in the data that delivers the largest differential between the two new nodes in terms of HIV positive status. The process then continues in each new node until a stopping criterion is reached.
This model identifies interesting subgroups - interactions which cannot be spotted by other methods such as logistic regression. The sample size of 33 800 was ideal for this method.
Monitoring of the implementation of the survey was conducted by technical teams from National, Provincial and District Health offices. This involved regular visits to sentinel sites, laboratories as well as addressing challenges arising during field execution.
A total of 33 927 out of the targeted 36 000 pregnant women attending antenatal care (ANC attendees) at selected public health facilities in the nine provinces in the country participated in survey during the month of October 2008. The sample population realization rate was 94.2 %. The analysis was done on 33 800 samples where 127 were excluded from the analysis because of missing data. The women were recruited from 1 408 in ANC clinics 2007 and 1 457 ANC clinics in 2008.
Table 1: Sample population distribution by age group, 2006 to 2008.
Not specified 217 0.7 182 0.5 102 0.
Total 33 034 100.
Age is an important risk factor, because it is central to monitoring the epidemic among the high sexually active group. The outcome of HIV prevalence in the 15 -24 years is crucial when reporting the outcome of the MDG 6, Target 7 Indicator 18. The age pattern of the women recruited in the survey was similar to the previous three surveys as shown in Table 1. About 50% of the respondents were young women aged 15 -24 years.
Half of the participants were women between aged 15 -24 years while 2.4% of the participants were women aged 35 years and above.
Almost 90% of the survey participants were African women. However, in the Western Cape (WC), the population group profile of participation in the survey was different from other provinces, the participation was almost equal between African and Coloureds. The population group distribution in WC was as follows: 50.8% (1 896) were African; 48.6% (1 817) were Coloured; 1 (one) Asian and 21 Whites. This will be carefully considered when interpreting future Western Cape HIV results. The distribution of the survey participants by population group and province are presented in Tables 2, and 3.
Table 2: Sample population distribution by population group, 2006 to 2008.
Coloured 3 045 9.2 3 010 8.9 2 930 8.
White 172 0.5 151 0.4 140 0.
Not specified 394 1.2 165 0.5 206 0.
Table 3: Demographic characteristics of the sample population by province, 2006 to 2008.
North West 2742 8.3 2 353 6.9 2 113 6.
Western Cape 3 866 11.7 3 830 11.3 3 848 11.
Total 33 034 100 33 685 100.0 33 927 100.
In the 2008 survey, the national overall HIV prevalence amongst 15 -49 years old antenatal women served in the public health clinics was 29.3% (95% CI: 28.5% - 30.1%). The estimated national HIV prevalence amongst the women surveyed has remained stable over the past three years: 29.1% in 2006; 29.4% in 2007 and 29.3% in 2008. This agrees with the recent projections by UNAIDS that the HIV epidemic curve is reaching a plateau. The HIV prevalence trend from 1990 to 2008 as shown in (Figure 2).
There is no significant change in the overall national HIV prevalence amongst South African pregnant women between 2006 and 2008, when looking at temporal trends. Findings from last year's survey confirm this pattern of stabilization with regards to the overall number of persons living with HIV in South Africa (Figure 3).
It is important to note that there is no significant evidence of an increase in HIV prevalence in the past three (3) years in South Africa. The three data set points for 2006 (n = 33 034); 2007 (n = 33 684) and 2008 (n = 33 927) indicating the plateuing of the HIV epidemic curve in the adult population in South Africa is shown (Figure 4).
The estimated national HIV prevalence by age group for 2008 and comparison with 2006 and 2007 is presented in Table 4. The HIV prevalence among women under the age of 25 years has remained stable over the past three years, this is in agreement with the total national HIV prevalence trend.
Table 4: HIV prevalence among antenatal women by age group, South Africa, 2006 to 2008.
The HIV prevalence estimates in the older age groups above 30 years, are showing a tendency towards an increase as seen in Figure 5. This could be a reflection of AIDS related mortality beginning to relent in this particular age group due to the provision of ARV treatment. Proper triangulation of such trends with AIDS related mortality by age in South Africa is necessary at this juncture to ensure a correct reading of where the country is with regards to its disease burden and ascertain the extent of the impact of interventions alluded to above.
Figure 5: HIV prevalence trends among antenatal women by age group, South Africa, 2006 to 2008.
The distribution of HIV prevalence ranged from 16.1% in the Western Cape to 38.7% in KwaZulu-Natal as shown in Figure 6. The results show that the highest HIV prevalences are located on the North-Eastern side, and the lowest prevalences in the Western parts of South Africa. KwaZulu-Natal still has the highest HIV prevalence followed closely by Mpumalanga, Free State and North West with overall prevalences greater than 30.0%. Gauteng, Limpopo and the Eastern Cape have prevalences between 20.0% and 30.0% and Northern Cape and Western Cape provinces have the lowest prevalences of below 20.0%.
In 2008, Free State, North West, Limpopo and Western Cape provinces showed a slight increase in HIV prevalence when compared to 2007, while KwaZulu-Natal, which had prevalence above 30%, remained static. The Gauteng, Eastern Cape and Northern Cape provinces are showing a tendency towards a decrease, although this is not statistically significant. Mpumalanga is the only province in the country for which the estimates are increasing from 32.1% in 2006 to 34.6% in 2007 and 35.5% in 2008 (Table 5 and Figure 7).
Figure 6: HIV prevalence distribution among antenatal women by province, South Africa 2008.
Table 5: HIV prevalence among antenatal women by province, South Africa, 2006 to 2008.
National 29.1 (28.3 -29.9) 29.4 (28.5 - 30.1) 12 783 455 29.3 (28.5 - 30.
Free State 31.1 (29.2 -33.1) 803 000 31.5 (29.1 -34.1) 802 218 32.9 (30.5 - 35.
North West 29.0 (26.9 -31.1) 986 000 30.6 (28.6 - 32.8) 856 138 31.0 (28.8 - 33.
Eastern Cape 28.6 (26.8 -30.4) 1 808 300 28.8 (26.9 - 30.7) 1 769 496 27.6 (25.6 - 29.
Northern Cape 15.6 (12.7 -18.5) 2 28 100 16.5 (13.9 - 19.6) 276 522 16.2 (13.7 - 18.
Western Cape 15.1 (11.6 -18.7) 1 309 100 15.3 (12.2 - 18.9) 1 327 334 16.1 (12.6 - 20.
District HIV prevalence has only been reported since 2006 when the geographic coverage of sentinel sites was increased and the sample size was doubled. There is a considerable variation in HIV prevalence between the 52 health districts observed over the three year period, particularly where the sample size is small, making it difficult to discern any trends.
In addition the districts are clearly heterogeneous with respect to the epidemic, with prevalence ranging from a high of over 45.0% to a low of around 2.2%. When data are pooled over the three years, 17 districts have a prevalence significantly higher than the mean prevalence (29.3%), while 20 out of the 52 are significantly below average The distribution of HIV prevalence by district in 2008, ranged from 2.2% in the district of Namakwa (Northern Cape) to 45.7% in uMgungundlovu (KwaZulu-Natal), recording the highest in the country. Out of the 52 health districts, 4 have prevalences above 40%, 18 have prevalences between 30% and 40%, 19 have prevalences between 20% and 30%, 9 have prevalences between 10% and 20% and 2 have prevalences below 10 %.
The least populated areas of South Africa and those most rural have recorded lower prevalences than the metropolitan areas. The HIV prevalence distribution among antenatal women by district, in 2006, 2007, 2008 and the average HIV distribution of the 3 years, is presented in Figure 8.
In Figure 8, the colour coding shown, reflects the intensity of the HIV prevalence among the pregnant women in the 52 health districts: Red are districts recording HIV prevalence above 40%. Orange are districts recording HIV prevalence between 30% and 40%, Mustard are districts recording HIV prevalence between 20% and 30%. Yellow are districts recording HIV have a prevalence between 10% and 20%. Light Yellow are districts recording HIV prevalence below 10 %.
For each province, comparison of the provincial and district HIV prevalences are reported from 2006 to 2008. Due to the smaller sample size in some districts the sampling error is much larger than at the provincial level. Therefore changes of 2% in either direction between the years within a district can be expected due to chance, if the sample size was less than 500.
In 2008, the KwaZulu-Natal provincial HIV prevalence amongst 15-49 year antenatal women was 38.7% (95% CI: 37.2% - 40.1%). KwaZulu-Natal has consistently recorded the highest prevalence since 1990. The epidemic curve shows evidence of stabilization in the past 3 years (Figure 9).
Three districts showed prevalences above 40% with uMgungundlovu recording an alarming 45.7%, meaning almost every second pregnant woman in that district is HIV positive! More than 50% (7/11) of the districts recorded prevalence above 30% (Figure 10 and Table 6). The distribution of HIV prevalence by district in KZN is shown in Figure 11.
Table 6: HIV prevalence among antenatal women by district, KwaZulu-Natal, 2006 to 2008.
Provincial 6 814 39.1 37.5 - 40.7 6 918 38.7 37.2 - 40.2 6 963 38.7 37.2 - 40.
In 2008, the Mpumalanga provincial HIV prevalence amongst 15-49 year antenatal women was 35.5% (95% CI: 33.1% - 37.9%). It is the only province that has shown an increase in the overall prevalence in the past three years from 32.1% in 2006 to 34.6% in 2007 and 35.5% in 2008, the highest it has recorded since the beginning of the epidemic (Figure 12).
When district results are compared, only Ehlanzeni district has shown a decrease in HIV prevalence, while the HIV prevalence in Gert Sibande district increased from 38.9 % in 2006 to 40.5% in 2008 and Nkangala from 26.8% in 2006 to 31.8% in 2008 (Table 7 and Figures 13 and14).
Table 7: HIV prevalence among antenatal women by district, Mpumalanga, 2006 to 2008.
Provincial 2 212 32.1 29.8 - 34.4 2 332 34.6 32.1 - 37.1 2 224 35.5 33.1 - 37.
In 2008, the Free State provincial HIV prevalence amongst 15-49 antenatal women was 32.9% (95% CI: 30.5% - 35.4%), which is an increase of more than one per cent from the previous years (Figure 15).
Four out of five (4/5) districts in the Free State recorded prevalence above 30% (Table 8 and Figure 16). All districts of the Free State province except Lejweleputswa which recorded a decrease in HIV prevalence from 37.0% in 2007 to 33.8% in 2008, have shown evidence of an increase from 2007 to 2008. Xhariep has increased from 19.7% in 2006 to 26.9% in 2008 (Figure 17).
Table 8: HIV prevalence among antenatal women by district, Free State, 2006 to 2008.
Provincial 2 225 31.1 29.2 - 33.1 2 167 31.5 29.1 -34.1 2 016 32.9 30.5 - 35.
In 2008, the Gauteng provincial HIV prevalence amongst 15-49 antenatal women was 29.9% (95% CI: 28.5% - 31.3%). The overall prevalence in Gauteng is beginning to show a slight decline from 30.8% in 2006 to 29.9% in 2008 (Figure 18).
It is evident that the overall HIV prevalence in Gauteng province has remained constant, with all districts showing a decrease in HIV prevalence during 2007 and 2008, except for City of Johannesburg, which has shown a slight increase from 29.9% in 2007 to 31.0 % in 2008 (Table 9 and Figure 19). The distribution of HIV prevalence by district in Gauteng province is shown in Figure 20.
Table 9: HIV prevalence among antenatal women by district, Gauteng, 2006 to 2008.
Provincial 6 145 30.8 29.6 -32.1 7 018 30.5 29.2 -31.9 7 497 29.9 28.5 - 31.
West Rand 405 34.6 30.0 -39.2 503 32.4 28.4 - 36.6 556 27.8 23.7- 32.
** Metsweding Health District was the only district not sampled in 2006 due to demarcation processes in North West Province. It was transferred to Gauteng Province in 2007.
In 2008, the North-West provincial HIV prevalence amongst 15-49 antenatal women was 31.0% (95% CI: 28.8% - 33.3%). The HIV prevalence in this province appears to be increasing from 29.0% in 2006, 30.6% in 2007 and 31.0% in 2008 (Figure 21).
Three out of the four (3/4) districts in the North West province have shown an increase in the past three years, except for Bojanala where the prevalence is beginning to show stabilization (Table 10 and Figure 22). In 2008 the highest HIV prevalence (35.2%) was recorded in the district of Dr. Kenneth Kaunda, while the lowest (28.1%) was seen in the district Dr. Ruth S. Mompati (see Figure 23).
Table 10: HIV prevalence among antenatal women by district, North West, 2006 to 2008.
Provincial 2 742 29.0 26.9 - 31.1 2 349 30.6 28.6 - 32.8 2112 31.0 28.8 - 33.
In 2008, the Eastern Cape provincial HIV prevalence amongst 15-49 antenatal women was 27.6% (95% CI: 25.6% - 29.6%). The overall HIV provincial prevalence in this province has decreased from 28.6% in 2006 to 27.6% in 2008 (Figure 24).
Ukhahlamba district prevalence has decreased significantly from 27.9% in 2006 to 21.9 % in 2008 (Table 11 and Figure 25). Only Alfred Nzo district showed an increase from 25.1% in 2006 to 29.8% in 2008. In 2007, Chris Hani and O.R. Tambo were the only districts recording prevalences above 30%. While in 2008 all districts recorded HIV prevalences below 30% (Figure 26).
Table 11: HIV prevalence among antenatal women by district, Eastern Cape, 2006 to 2008.
Provincial 4 074 28.6 26.8 -30.4 4 118 28.8 26.9 -30.7 4 216 27.6 25.6 - 29.
Figure 25: HIV prevalence trends among antenatal women by district, Eastern Cape 2006 to 2008.
Figure 27: HIV prevalence epidemic curve among antenatal women, Limpopo, 1990 to 2008.
The HIV prevalence has remained relatively stable since 2006. Sekhukhune showed an increase of 5.7% from 16.1% in 2006 to 21.8% in 2008. Waterberg district has shown a slight decline from 27.5% in 2006 to 23.6% in 2008 (Table 12 and Figure 28). The HIV prevalence distribution by district in Limpopo is shown in Figure 29.
Table 12: HIV prevalence among antenatal women by district, Limpopo, 2006 to 2008.
Provincial 3 869 20.6 18.9 -22.3 3 748 20.4 18.9 - 21.9 3 833 20.7 19.1 - 22.
In 2008, the Northern Cape provincial HIV prevalence amongst 15-49 antenatal women was 16.2% (95% CI: 13.8% - 18.9%). The prevalence has varied by less than 1% in the past 3 years, and has shown stabilization between 2007 and 2008 (Figure 30).
Namakwa district has consistently recorded the lowest HIV prevalence (2.2% in 2008) in the whole country. Frances Baard recorded the highest HIV prevalence (21.8%) in the province in 2008 (Figure 31 and 32). Interestingly, this province has recorded the highest syphilis prevalence among all the other provinces in the past 3 years (see section on syphilis results). This requires further epidemiological investigation to determine the cause of this variation.
Provincial 1087 15.6 12.7 -18.5 1190 16.5 13.9 - 19.6 1111 16.2 13.8 - 18.
In 2008, the Western Cape provincial HIV prevalence amongst 15 -49 antenatal women was 16.1% (95% CI: 12.6% - 20.3%). The overall HIV prevalence has increased from 15.1% in 2006 to 16.1% in 2008, (Figure 33).
The Central Karoo district has shown a significant increase, from 8.3% in 2006 to 23.6% in 2007 (15.3%). However, there was a sudden 8.8% decrease in HIV prevalence in the same district in 2008 (Table 14 and Figure 34). The distribution of HIV prevalence by district (Figure 35) shows that West-Coast district has the lowest HIV prevalence in the Western Cape Province and it is the second lowest after Namakwa (Northern Cape) in the country.
Table 14: HIV prevalence among antenatal women by district, Western Cape, 2006 to 2008.
Provincial 3 866 15.1 11.6 - 18.7 3 830 15.3 12.2 - 18.9 3 828 16.1 12.6 - 20.
West Coast 232 7.3 4.0 -10.7 206 10.1 7.2 - 14.2 204 9.3 6.2 - 13.6 3.
Districts HIV prevalence is clearly heterogeneous, with prevalence ranging from a high of over 45% to a low of around 2.2%. When data are pooled over the three years, 17 districts have a prevalence significantly higher that the mean prevalence, while 20 out of the 52 are significantly below average.
Four districts (7.6%) recorded HIV prevalences above 40% in 2008. Thirty two per cent (17/52) of the districts recorded HIV prevalences between 30% and 40%. Six were located in KwaZulu-Natal, three in Gauteng, four in Free State, two in Mpumalanga and the remaining two in North West. Interestingly, no district in the Eastern Cape has recorded HIV prevalences above 30% in 2008 (Figure 39).
Nineteen (36%) out of 52 health districts in the country recorded district HIV prevalences between 20.0% and 30.0%. This included all districts (seven) in the Eastern Cape four in Limpopo, three in Gauteng, two in North West province and one in KwaZulu-Natal, Northern Cape and Free State provinces.
Only 17% (9/52) of the 52 health districts recorded prevalence between 10% and 20%. Five were districts located in Western Cape, three located in the Northern Cape and one in Limpopo. Namakwa district in the Northern Cape and West Coast district in the Western Cape recorded the lowest district HIV prevalence in the country. Appendix D and E provides the detail description of HIV prevalence distribution by districts in 2006 and 2007.
The 2008 survey found that 1.9% CI 95% (1.7 - 2.0) of pregnant women presenting at public antenatal care clinics were infected with syphilis. This is lower than the 2.
(2.6 - 3.0) recorded for 2007. The trend of syphilis prevalence among attendees of antenatal clinics from 1997 to 2007 is shown in Figure 37 below. Since 2003 the national estimate has been fluctuating between a prevalence of 1.6 and 2.8%.
Reading from Table 15, the estimated syphilis prevalence in the Northern Cape for 2008 is 6.8%. The Northern Cape is the province with the highest syphilis prevalence, this has been the case over the past 3 years with a prevalence of 6.9% in 2006, 5.4% in 2007, 6.8% in 2008.
There was a significant increase in syphilis prevalence in the Western Cape province from 1.9% in 2006 to 5.6 % in 2007, (more than double), but it dropped quite a bit in 2008 to 3.8%. Western Cape, Gauteng, Mpumalanga, Eastern Cape, North West and Limpopo all experienced an increase in syphilis prevalences from 2006 to 2007. However, in 2008, all of these provinces except Northern Cape showed reductions in prevalence. Mpumalanga syphilis prevalence has more than halved from 1.8 % in 2007 to 0.
Table 15: Syphilis prevalence by province among antenatal women, South Africa, 2006 to 2008.
National 1.8 (1.7 -2.0) 2.8 (2.6 - 3.0) 1.9 (1.7 - 2.
Northern Cape 6.9 (5.0 -8.9) 5.4 (4.2 - 6.9) 6.8 (5.2 - 8.
Western Cape 1.9 (1.4 -2.4) 5.6 (4.9 - 6.3) 3.8 (3.1 - 4.
Free State 2.5 (1.8 -3.1) 2.5 (1.9 - 3.0) 2.3 (1.7 - 3.
Eastern Cape 2.6 (2.0 -3.1) 3.0 (2.5 - 3.6) 1.9 (1.5 - 2.
North West 1.8 (1.2 -2.4) 2.7 (2.1 - 3.5) 1.5 (1.1 - 2.
Provinces with high HIV prevalences show low syphilis prevalences and vice versa. Northern Cape still records the highest syphilis prevalence and the lowest HIV prevalence. KwaZulu-Natal, which has the highest HIV prevalence in the country, has the second lowest syphilis prevalence (Figure 38).
Figure 39 shows the syphilis prevalence by age group. There was an increase in prevalence in EVERY age group in 2007 and this certainly warrants further investigation in order to answer two questions "Why the spike and "What could have been happening in the last 6 years?
Potential HIV risk factors may act independently or concurrently to drive the HIV epidemic. Identification of independent factors related to a positive HIV infection status was determined through classification tree regression.
The first and best split was on age at 21 years where women <=21 years had HIV prevalence of 16.8% compared to the 34.8% HIV prevalence among women 22 years and older. This split of the overall group with prevalence of 29.2% has identified a younger subgroup that has a much lower prevalence. No further splits were identified in this group of young women.
In the older group the next split was on race. An African subgroup (37.6%) is identified versus the rest (6.8%) of White, Asian and Coloured women which has a low prevalence and no further splits were identified.
The model then looks at African women >=22 years. Education was found to be the most important splitter for this subgroup at grade 11 or less versus grade 12 or more. Lower HIV prevalence was found in the higher education level.
The model does not show any 'startling' results - although the cut off points that come to the fore were interesting i.e. age 21 years. One important observation was the absence of syphilis infection in the model. Therefore, the joint outcome of HIV and RPR is not that important in the larger picture (in determining the HIV status of antenatal women). The performance of the prediction model is modest (slightly better than chance) with an overall correct classification of 60%, a sensitivity of 74% and specificity of 55%. The model did not incorporate any geographical information such as province or district. It can be seen as a model to classify any first time attendee walking through a clinic door as HIV positive or not given her basic demographic information.
UNAIDS uses EPP to estimate the HIV trends over time by fitting an epidemiological model to the surveillance data provided by HIV sentinel surveillance systems. Separate estimates and time trends are developed for each of the provinces, they are then combined within EPP to produce a national estimate for HIV prevalence and its trends over time. The HIV estimation process through UNAIDS Spectrum and EPP Models is presented in Appendix E.
Sentinel surveillance and population-based surveys have strengths and weaknesses but taken together provide complementary information and can provide a clear picture of both overall trends and geographical distribution of HIV. Results from both populationbased survey and antenatal sentinel surveillance are used to adjust estimates to bias identified in both surveys. The 2008 HIV prevalence estimates projected from the three mathematical models, UNAIDS, ASSA and HSRC are shown in Figure 40 and Table 16. It is encouraging to see that the estimated number of adult new infections (incidence) are estimated to be 380 000 and paediatric HIV incidence 56 000 in 2008.