Interpreting HIV seroprevalence data from pregnant women

A Comparative Study of the Epidemiology of Treponemal Infection in the Volta and Oti Regions of Ghana: A Five-Year Multisite Parallel Population-Based Analysis vis-à-vis the Sentinel Survey

Treponemal infections can be blood-borne with great public health consequences. This study is aimed at comparatively describing the five-year (2013-2017) regional epidemiology of treponemal infection using pregnant women in the sentinel survey and apparently healthy blood donors as a proxy for the general population at four sentinel sites in the Volta and Oti Regions of Ghana. We analyzed retrospective data from 17,744 prospective blood donors aged 18 to 58 years and 7,817 pregnant women in a sentinel survey with ages from 15 to 49 years at Hohoe, Ho, Tongu, and Krachi West sentinel sites in the Volta and Oti Regions. Laboratory data extracted include variables such as age, gender, date of blood donation, and Treponema pallidum chromatographic immunoassay results from the blood banks of the four study sites. The five-year treponemal infection rate among the pregnant women in the sentinel survey and prospective blood donors was 0.79% and 2.38%, respectively. Site-specific infection rate for population-based/sentinel survey was 4.6%/1.1%, 2.0%/0.5%, 1.3%/1.1, and 1.2%/0.3% for Hohoe, Ho, Krachi West, and Tongu, respectively. Significant gender disparity in Treponemal infection rate exists with a male preponderance. The regional infection rate in the sentinel survey is lower compared to the general population. Therefore, the use of pregnant women as a proxy for population estimates could underestimate the burden in the study jurisdiction.

Capturing the spatial variability of HIV epidemics in South Africa and Tanzania using routine healthcare facility data

BACKGROUND

Large geographical variations in the intensity of the HIV epidemic in sub-Saharan Africa call for geographically targeted resource allocation where burdens are greatest. However, data available for mapping the geographic variability of HIV prevalence and detecting HIV 'hotspots' is scarce, and population-based surveillance data are not always available. Here, we evaluated the viability of using clinic-based HIV prevalence data to measure the spatial variability of HIV in South Africa and Tanzania.

METHODS

Population-based and clinic-based HIV data from a small HIV hyper-endemic rural community in South Africa as well as for the country of Tanzania were used to map smoothed HIV prevalence using kernel interpolation techniques. Spatial variables were included in clinic-based models using co-kriging methods to assess whether cofactors improve clinic-based spatial HIV prevalence predictions. Clinic- and population-based smoothed prevalence maps were compared using partial rank correlation coefficients and residual local indicators of spatial autocorrelation.

RESULTS

Routinely-collected clinic-based data captured most of the geographical heterogeneity described by population-based data but failed to detect some pockets of high prevalence. Analyses indicated that clinic-based data could accurately predict the spatial location of so-called HIV 'hotspots' in > 50% of the high HIV burden areas.

CONCLUSION

Clinic-based data can be used to accurately map the broad spatial structure of HIV prevalence and to identify most of the areas where the burden of the infection is concentrated (HIV 'hotspots'). Where population-based data are not available, HIV data collected from health facilities may provide a second-best option to generate valid spatial prevalence estimates for geographical targeting and resource allocation.

Discordant HIV Test Results: Implications on Perinatal and Haemotransfusion Screening for HIV Infection, Cape Coast, Ghana

Screening results of 488 pregnant women aged 15–44 years whose blood samples had been tested on-site, using First Response® HIV 1/2, and confirmed with INNO-LIA™ HIV I/II Score were used. Of this total, 178 were reactive (HIV I, 154; HIV II, 2; and HIV I and HIV II, 22). Of the 154 HIV I-reactive samples, 104 were confirmed to be HIV I-positive and 2 were confirmed to be HIV II-positive, while 48 were confirmed to be negative [false positive rate = 17.44% (13.56–21.32)]. The two HIV II samples submitted were confirmed to be negative with the confirmatory test. For the 22 HIV I and HIV II samples, 7 were confirmed to be HIV I-positive and 1 was confirmed to be HIV I- and HIV II-positive, while 14 were confirmed to be negative. Of the 310 nonreactive samples, 6 were confirmed to be HIV I-positive and 1 was confirmed to be HIV II-positive [false negative rate = 5.79% (1.63–8.38)], while 303 were negative. False negative outcomes will remain unconfirmed, with no management options for the client. False negative rate of 5.79% requires attention, as its resultant implications on control of HIV/AIDS could be dire.

High HIV Prevalence among Asylum Seekers Who Gave Birth in the Netherlands: A Nationwide Study Based on Antenatal HIV Tests

OBJECTIVES

Asylum seekers are considered to be a particularly vulnerable group with respect to HIV. Data on the HIV prevalence among asylum seekers, however, are scarce. The aim of this study is to map the HIV prevalence among asylum seekers who gave birth in The Netherlands.

METHODS

We used a nationwide electronic medical records database from the community health services for asylum seekers (MOA). The study population consisted of 4,854 women and girls who delivered in asylum reception between 2000 and 2008. A unique electronic health data base was used and case allocation was based on ICPC-codes.

RESULTS

The number of women and girls that was HIV positive during their last pregnancy was 80, of which 79 originated from sub-Saharan Africa. The prevalence for women from this region of origin (3.4%) was high compared to women from all other regions of origin (0.04%; OR = 90.2; 95%CI 12.5-648.8). The highest HIV prevalence rates were found for women from Rwanda (17.0%) and Cameroon (13.2%). HIV prevalence rates were higher among women who arrived in reception without partner (OR = 1.82; 95%CI 0.75-4.44) and unaccompanied minors (OR = 2.59; 95%CI 0.79-8.49), compared to women who arrived in reception with partner.

CONCLUSIONS

We conclude that, among asylum-seeking women from sub-Saharan Africa giving birth in The Netherlands, the HIV prevalence is high compared to the host population. For women from other regions of origin, the prevalence is at the same level as in the host population. The high HIV prevalence underlines the importance of preventive interventions and voluntary HIV testing for sub-Saharan African asylum seekers as from shortly after arrival.

[HIV infection among pregnant women attended in testing and counseling centers for AIDS]

OBJECTIVE

To estimate HIV prevalence and identify high-risk sexual behavior for infection in pregnant women who were given prenatal assistance.

METHODS

Cross-sectional study based on attendance records of 8,002 pregnant women (25% of all municipalities) who lived in 27 municipalities in Southern Brazil in 2003 and had anti-HIV tests done in a testing and counseling center that performed prenatal assistance. Sociodemographic and behavioral data were gathered, as well as syphilis and HIV test results, during the individual counseling sessions registered in the data bank of the Sistema de Informações dos Centros de Testagem e Aconselhamento (Information System on Testing and Counseling Centers). Women who sought the centers for confirmation of previous serology or were referred to this service due to the presence of AIDS symptoms were excluded from the data base.

RESULTS

A total of 0.5% of all the pregnant women analyzed (CI 95%=0.3;0.6) were HIV positive. The only variable associated with HIV seropositivity was schooling. The majority of them were basically exposed through unprotected sexual intercourse with the only partner they had a steady relationship with. Younger pregnant women who were single, unemployed and had lower level of education constituted the group with highest exposure.

CONCLUSIONS

The Sistema de Informações dos Centros de Testagem e Aconselhamento turned out to be useful for the epidemiological surveillance of HIV infection and high-risk behavior among pregnant women and could also be useful as regards other populations.

Association between fertility and HIV status: what implications for HIV estimates?

BACKGROUND

Most estimates of HIV prevalence have been based on sentinel surveillance of pregnant women which may either under-estimate or over-estimate the actual prevalence in adult female population. One situation which can lead to either an underestimate or an overestimate of the actual HIV prevalence is where there is a significant difference in fertility rates between HIV-positive and HIV-negative women. Our aim was to compare the fertility rates of HIV-infected and HIV-uninfected women in Cameroon in order to make recommendations on the appropriate adjustments when using antenatal sentinel data to estimate HIV prevalence.

METHODS

Cross-sectional, population-based study using data from 4493 sexually active women aged 15 to 49 years who participated in the 2004 Cameroon Demographic and Health Survey.

RESULTS

In the rural area, the age-specific fertility rates in both HIV positive and HIV negative women increased from 15-19 years age bracket to a maximum at 20-24 years and then decreased monotonically till 35-49 years. Similar trends were observed in the urban area. The overall fertility rate for HIV positive women was 118.7 births per 1000 woman-years (95% Confidence Interval [CI] 98.4 to 142.0) compared to 171.3 births per 1000 woman-years (95% CI 164.5 to 178.2) for HIV negative women. The ratio of the fertility rate in HIV positive women to the fertility rate of HIV negative women (called the relative inclusion ratio) was 0.69 (95% CI 0.62 to 0.75).

CONCLUSION

Fertility rates are lower in HIV-positive than HIV-negative women in Cameroon. The findings of this study support the use of summary RIR for the adjustment of HIV prevalence (among adult female population) obtained from sentinel surveillance in antenatal clinics.

Antenatal clinic HIV data found to underestimate actual prevalence declines: evidence from Zambia

OBJECTIVE

To determine to what extent antenatal clinic (ANC)-based estimates reflect HIV prevalence trends among men and women in a high prevalence urban population.

METHODS

Examination of data from serial population-based HIV surveys in 1995 (n = 2115), 1999 (n = 1962) and 2003 (n = 2692), and ANC-based surveillance in 1994 (n = 450), 1998 (n = 810) and 2002 (n = 786) in the same site in Lusaka, Zambia. The population-based surveys recorded refusal rates between 6% and 10% during the three rounds.

RESULTS

Among ANC attendees, prevalence declined by 20% (25.0% to 19.9%; P = 0.101) in the age group 15-24 years and was stable overall. In the general population, the prevalence declined by 49% (P < 0.001) and by 32% (P < 0.001) in age group 15-24 and 15-49, respectively. Among women only, HIV prevalence declined by 44% (22.5% to 12.5%; P < 0.001) and by 27% (29.6% to 21.7%; P < 0.001) in age group 15-24 and 15-49 years, respectively. In addition, prevalence substantially declined in higher educated women aged 15-24 years (20.7% to 8.5%, P < 0.001).

CONCLUSION

ANC-based estimates substantially underestimated declines in HIV prevalence in the general population. This seemed to be partially explained by a combination of marked differentials in prevalence change by educational attainment and changes in fertility-related behaviours among young women. These results have important implications for the interpretation of ANC-based HIV estimates and underscore the importance of population-based surveys.

Can data from programs for the prevention of mother-to-child transmission of HIV be used for HIV surveillance in Kenya?

OBJECTIVE

In Africa, HIV surveillance is conducted among antenatal clinic (ANC) attendees using unlinked-anonymous testing (UAT). In Kenya, the utility of prevention of mother-to-child transmission (PMTCT) program data for HIV surveillance was evaluated.

METHODS

UAT and PMTCT data were compared at the same clinics and for the same time (2003 UAT survey) period. The HIV testing uptake for PMTCT was defined as the number of ANC attendees tested for HIV out of those who had their first ANC visit during the ANC surveillance period. Odds ratios and 95% confidence intervals were calculated to determine associations between demographic characteristics and HIV testing acceptance.

RESULTS

Of 39 ANC-UAT sites, six had PMTCT data. PMTCT data were recorded across several logbooks with varying quality. For PMTCT, 2,239 women were offered HIV testing and 1,258 (56%) accepted; for UAT, 1,852 women were sampled. Median UAT-based HIV prevalence was 12.8% (range, 8.1%-26.3%) compared with 14.4% (range, 7.0%-27.2%) in PMTCT. HIV testing acceptance for PMTCT ranged from 48% to 69% across clinics, and was more likely among primigravidae than multigravidae.

CONCLUSION

Because of varying PMTCT data quality and varying HIV testing acceptance for PMTCT, PMTCT-based HIV prevalence estimates cannot currently replace UAT-based estimates in Kenya.

Steep HIV prevalence declines among young people in selected Zambian communities: population-based observations (1995-2003)

BACKGROUND

Understanding the epidemiological HIV context is critical in building effective setting-specific preventive strategies. We examined HIV prevalence patterns in selected communities of men and women aged 15-59 years in Zambia.

METHODS

Population-based HIV surveys in 1995 (n = 3158), 1999 (n = 3731) and 2003 (n = 4751) were conducted in selected communities using probability proportional to size stratified random-cluster sampling. Multivariate logistic regression and trend analyses were stratified by residence, sex and age group. Absence, <30% in men and <15% in women in all rounds, was the most important cause of non-response. Saliva was used for HIV testing, and refusal was <10%.

RESULTS

Among rural groups aged 15-24 years, prevalence declined by 59.2% (15.7% to 6.4%, P < 0.001) in females and by 44.6% (5.6% to 3.1%, P < 0.001) in males. In age-group 15-49 years, declines were less than 25%. In the urban groups aged 15-24, prevalence declined by 47% (23.4% to 12.4%, P < 0.001) among females and 57.3% (7.5% to 3.2%, P = 0.001) among males but were 32% and 27% in men and women aged 15-49, respectively. Higher educated young people in 2003 had lower odds of infection than in 1995 in both urban [men: AOR 0.29(95% CI 0.14-0.60); women: AOR 0.38(95% CI 0.19-0.79)] and rural groups [men: AOR 0.16(95% CI 0.11-0.25), women: AOR 0.10(95% CI 0.01-7.34)]. Although higher mobility was associated with increased likelihood of infection in men overall, AOR, 1.71(95% CI 1.34-2.19), prevalence declined in mobile groups also (OR 0.52 95% CI 0.31-0.88). In parallel, urban young people with > or =11 school years were more likely to use condoms during the last casual sex (OR 2.96 95% CI 1.93-4.52) and report less number of casual sexual partners (AOR 0.33 95% CI 0.19-0.56) in the last twelve months than lower educated groups.

CONCLUSION

Steep HIV prevalence declines in young people, suggesting continuing declining incidence, were masked by modest overall declines. The concentration of declines in higher educated groups suggests a plausible association with behavioural change.

A high prevalence of HIV-1 infection among pregnant women living in a rural district of north Uganda severely affected by civil strife

This study aims at estimating the recent trends in HIV-1 prevalence and the factors associated with infection among pregnant women in the Gulu District of north Uganda, a rural area severely affected by civil strife. In 2000-2003, a total of 4459 antenatal clinic attendees of Lacor Hospital were anonymously tested for HIV-1 infection. The overall and age-specific prevalence did not show any significant trend over time. The age-standardized prevalence slightly declined, from 12.1% in 2000 to 11.3% in 2003. Increased age [20-24 years: adjusted odds ratio (AOR) 1.63; 95% CI 1.18-2.25; >or=25 years: AOR 2.56; 95% CI 1.91-3.44], residence in urban areas (AOR 1.76; 95% CI 1.41-2.18), being unmarried (AOR 1.60; 95% CI 1.27-2.01), increased age of partner (25-34 years: AOR 1.87; 95% CI 1.29-2.73; >or=35 years: AOR 2.68; 95% CI 1.72-4.16), modern occupation of partner (AOR 1.98; 95% CI 1.53-2.58), and short time of residence at the current address (AOR 1.36; 95% CI 1.05-1.76) were associated with infection. The HIV-1 prevalence in this rural district is high and similar to that observed in urban antenatal clinics, probably reflecting the effect of the last 18 years of civil strife.

Evaluating two adjustment methods to extrapolate HIV prevalence from pregnant women to the general female population in sub-Saharan Africa

OBJECTIVE

To evaluate two methods for estimating HIV prevalence among the general female population of reproductive age by adjusting data observed among antenatal clinic (ANC) attendees.

METHODS

We adjusted the HIV prevalence among ANC attendees in Fort Portal (Uganda; 1994-1995), Mwanza municipality (Tanzania; 1990-1991), rural Mwanza (Tanzania; 1991-1993), Mposhi district (Zambia; 1994), Chelston (Lusaka, Zambia; 1994, 1996 and 1998) and Ndola (Zambia; 1998), using firstly a method that accounts for differences in age-specific fertility by HIV serostatus and secondly a method that accounts for differences in HIV prevalence by fertility risk category and parity.

RESULTS

The non-adjusted HIV prevalence among ANC attendees underestimates the prevalence among the general female population by 8.0% in Chelston in 1998 and by between 20.7% and 31.9% in all other cases. The adjusted prevalence obtained using the first method underestimates the prevalence among the general female population by about 0.5% in Fort Portal and Mposhi; it overestimates that observed in Chelston in 1994 and 1996 by about 3.5%, and that observed in Ndola, urban Mwanza and rural Mwanza, by 6.5%, 10.6% and 12.8%, respectively. The second method (applied for only four sites) provides an overestimate of 7.0% in Chelston in 1994 and an underestimate of 3.8% and 2.1% in Ndola and rural Mwanza, respectively. Both adjustment methods overestimate the 1998 prevalence in Chelston, producing less accurate estimates than the non-adjusted data.

CONCLUSIONS

The HIV prevalence among women in the general population could be estimated fairly accurately by these methods in settings with mature epidemics.

Reproductive behaviour of HIV-infected women living in France, according to geographical origin

Pregnancy rates were compared before and after HIV diagnosis according to geographical origin (sub-Saharan Africa versus Europe) among 533 HIV-infected women followed in the French SEROCO/SEROGEST cohorts between 1988 and 1996. Among European women, the incidence of deliveries and terminations decreased, respectively, by nearly twofold and fourfold after HIV diagnosis. Conversely, the pregnancy incidence increased among African women with fewer than two children. This study should help refine the reproductive counselling and management of HIV-infected women in France.

Factors influencing the difference in HIV prevalence between antenatal clinic and general population in sub-Saharan Africa

OBJECTIVE

To compare HIV prevalence in antenatal clinics (ANC) and the general population, and to identify factors determining the differences that were found.

DESIGN

Cross-sectional surveys in the general population and in ANC in three cities.

METHODS

HIV prevalence measured in adults in the community was compared with that measured by sentinel surveillance in ANC in Yaoundé, Cameroon, Kisumu, Kenya, and Ndola, Zambia.

RESULTS

In Yaoundé and Ndola, the HIV prevalence in ANC attenders was lower than that in women in the population overall, and for age groups over 20 years. In Kisumu, the HIV prevalence in ANC attenders was similar to that in women in the population at all ages. The only factors identified that influenced the results were age, marital status, parity, schooling, and contraceptive use. The HIV prevalence in women in ANC was similar to that in the combined male and female population aged 15-40 years in Yaoundé and Ndola, but overestimated it in Kisumu. In Yaoundé and Ndola, the overall HIV prevalence in men was approximated by using the age of the father of the child reported by ANC attenders, but this method overestimated the HIV prevalence in Kisumu, and did not give good age-specific estimates.

CONCLUSION

Few factors influenced the difference in HIV prevalence between ANC and the population, which could aid the development of adjustment procedures to estimate population HIV prevalence. However, the differences between cities were considerable, making standard adjustments difficult. The method of estimating male HIV prevalence should be tested in other sites.

Trend in HIV-1 prevalence in an antenatal clinic in North Uganda and adjusted rates for the general female population

OBJECTIVES

To estimate HIV-1 prevalence among women attending an antenatal clinic in the Gulu District (North Uganda) and, based on these data, among the district's female population.

METHODS

Anonymous HIV-1 screening was performed for 8555 antenatal clinic attendees aged 15-39 years in the period 1993-1997. The results were used to estimate the prevalence among the district's female population, accounting for differences in fertility rates by HIV-1 serostatus.

RESULTS

Among antenatal clinic attendees, HIV-1 prevalence showed a significant linear decrease (P < 0.001), from 26.0% in 1993 [95% confidence Interval (CI), 23.2-29.0%] to 16.1% in 1997 (95% CI, 14.8-17.5%). This decrease was mostly due to a marked decrease until 1995 (14.3%; 95% Cl, 12.7-16.0%) and was more pronounced among women aged under 30 years (P < 0.001), from both urban and rural areas (P < 0.001). The risk of being infected was higher among women from urban areas (Gulu Municipality), both over the entire period (adjusted prevalence proportion ratio = 1.54; 95% CI, 1.40-1.68) and by individual year. The estimated prevalence for the 15-39-year-old female population, standardized by age and area of residence, decreased from 25.4% in 1993-1994 to 17.8% in 1996-1997; these rates were 1.22 and 1.28 times higher, respectively, than those among antenatal clinic attendees.

CONCLUSIONS

The trend of decrease among young women, for whom changes in HIV-1 prevalence more closely reflect incidence, could be partially due to a reduction in risk behaviour and a consequent decreasing incidence. Differences in fertility rates by HIV-1 serostatus should be addressed when using antenatal clinic data to estimate prevalence among the general female population.

Adjusting ante-natal clinic data for improved estimates of HIV prevalence among women in sub-Saharan Africa

OBJECTIVES

To find a simple and robust method for adjusting ante-natal clinic data on HIV prevalence to represent prevalence in the general female population in the same age range, allowing for fertility differences by HIV status.

BACKGROUND

HIV prevalence comparisons for pregnant women and women in the general community show that prevalence in the latter is significantly higher than in the former. An adjustment procedure is needed that is specific for the demographic and epidemiological circumstances of a particular population, making maximum use of data that can easily be collected in ante-natal clinics or are widely available from secondary sources.

METHODS

Birth interval length data are used to allow for subfertility among HIV-positive women. To allow for infertility, relative HIV prevalence ratios for fertile and infertile women obtained in community surveys in populations with similar levels of contraception use are applied to demographic survey data that describe the structure of the population not at risk of child-bearing.

RESULTS

For populations with low contraception use, the procedure yields estimates of general female HIV prevalence of 35-65% higher than the observed ante-natal prevalence, depending on population structure. Results were verified using general population prevalence data collected in Kisesa (Tanzania) and Masaka (Uganda). For high contraception use populations, adjusted values range from 15% higher to 5% lower, but only limited verification has been possible so far.

CONCLUSIONS

The procedure is suitable for estimating general female HIV prevalence in low contraception use populations, but the high contraception variant needs further testing before it can be applied widely.

Monitoring of HIV-1 infection prevalence and trends in the general population using pregnant women as a sentinel population: 9 years experience from the Kagera region of Tanzania

In the Kagera region of Tanzania, a population-based study was initiated in 1987 followed by the establishment of antenatal-clinic-based sentinel surveillance system in the town of Bukoba in 1990. Repeat studies in both populations in Bukoba in 1993 and 1996 made it possible to study the dynamics of HIV infection prevalence and incidence in the area. This study aims at comparing the findings from this sentinel surveillance system with those of cross-sectional studies in the general population to assess its validity in estimating HIV prevalence and their trends in the general population. A multistage cluster sampling technique was used in the population-based studies whereas the antenatal-clinic-based population was obtained by consecutively recruiting antenatal care attenders coming for the first time during a given pregnancy. Antibodies against HIV infection were tested using two independent enzyme-linked immunosorbent assay (ELISA) antibody detection tests. Unlinked anonymous testing strategy was adopted for the sentinel population. Age-adjusted prevalence among antenatal care attenders decreased from 22.4% (95% confidence interval [CI], 20.6-25.2) in 1990 to 16.1% (95% CI, 15.9-18.8) in 1993 and further to 13.7% (95% CI, 11.8-14.3) in 1996. These results closely resemble those of the general population of adult women in the clinic's catchment area (the town of Bukoba) where the age-adjusted prevalence of 29.1% (95% CI, 24.4-34.6) in 1987 showed a decrease in the studies in 1993 18.7% (95% CI, 15.1-23.0) and in 1996 14.9% (95% CI, 12.0-17.1). The study indicates that general population trend estimates can be generated using sentinel surveillance data based on pregnant women visiting an antenatal clinic for the first time during a given pregnancy. The benefits of using this group outweigh its limitations that are brought about by possible selection bias. Continued surveillance of the epidemic based on antenatal care patients as a sentinel population is therefore recommended.

Estimativa do número de pessoas de 15 a 49 anos infectadas pelo HIV, Brasil, 1998

Neste trabalho, estima-se o número de indivíduos de 15-49 anos infectados pelo HIV no Brasil, em 1998, com base nos dados dos estudos de população-sentinela em gestantes que apresentavam viés de seleção da amostra. Um procedimento de componentes principais foi usado para agregar 44 municípios em 13 conglomerados homogêneos. Para cada conglomerado foram construídos dois indicadores: a) logaritmo da taxa de incidência acumulada de AIDS entre mulheres de 15-34 anos de idade (1996) e b) logaritmo da razão de crescimento da taxa de incidência média de AIDS em mulheres de 15 a 34 anos, do período de 1990-1992 para 1993-1996. Tendo como variável resposta o logito da proporção de gestantes infectadas pelo HIV e como variáveis independentes os dois indicadores citados, ajustou-se uma reta de regressão aos dados agregados. A estimação dos parâmetros do modelo permitiu calcular a proporção de infectados por grande região, por idade (15-34 e 35-49 anos) e por sexo. A estimativa por ponto foi de 536 mil adultos infectados pelo HIV com intervalo de confiança de 68% (470.689; 603.305).

Low and stable HIV infection rates in Senegal: natural course of the epidemic or evidence for success of prevention?

OBJECTIVES

To document the level of HIV infection in Senegal and also to review evidence of the impact of efforts in prevention, developed by the National AIDS Control Programme and the Civil Society, on the level of the HIV epidemic.

METHODS

Research, compilation and critical review of all relevant data on HIV and sexually transmission diseases (STDs) epidemiology, sexual behaviour, and the efforts in prevention developed in Senegal.

RESULTS

From 1989 to 1996, the levels of HIV infection estimated in four sentinel urban regions remained stable at around 1.2% in the population of pregnant women, and at 3% in male STD patients. It had increased to 19% in female sex workers. A strong political and community commitment led to an early response to the HIV/AIDS epidemic that has been extended since 1986. Blood transfusion safety was established at the start of the HIV epidemic. The level of knowledge of preventive practices relating to HIV/AIDS among the general population exceeded 90% in the early 1990s. From 1991 to 1996, a 30% to 66% decrease of the STD prevalence rates was observed in pregnant women and sex workers in Dakar. In 1997, 33% of men aged 15-49 years in Dakar reported having had sex with non-regular partners. Among them 67% reported condom use.

CONCLUSIONS

It is not possible to know what the course of the HIV epidemic in Senegal would have taken in the absence of efforts at prevention. Certainly, several factors that pre-dated the occurrence of AIDS in Senegal laid the groundwork for a positive response. However, data from a number of sources do reveal the successfulness of efforts in prevention. From available data, Senegal can rightfully claim to have contained the spread of HIV by intervening early and comprehensively to increase knowledge and awareness of HIV/AIDS and to promote safe sexual behaviour.

The relationship of HIV prevalence in pregnant women to that in women of reproductive age: a validated method for adjustment

OBJECTIVE

To devise and validate a method for adjusting HIV seroprevalences in pregnant women to estimate population prevalences among all women in their child-bearing years.

DESIGN

Birth and termination rates from women with known HIV infection in the United Kingdom were calculated according to the likely route of HIV infection and whether HIV infection was diagnosed.

METHODS

Birth and termination rates were weighted and combined to produce summary statistics. Comparisons were then made with population birth and termination rates to derive summary relative inclusion ratios (RIRs), the relative probabilities of including HIV-infected and uninfected women in seroprevalence surveys of pregnant women.

RESULTS

The derived RIRs for women having live births were close to unity: 1.03 [95% confidence intervals (CI) 0.90-1.17] for London and 0.80 (Cl, 0.71-0.89) for elsewhere in England and Wales. This indicates that currently observed overall seroprevalences among pregnant women having live births in London would be similar to those among all women of the same age, while elsewhere it would be slightly underestimated. Sensitivity analysis indicated that RIRs could, however, vary three-fold (0.47-1.56) according to the proportion of diagnosed maternal infections and the mix of maternal HIV-exposure categories. The method was validated by using it to predict the ratio of unlinked seroprevalences between women having terminations and live births in London. It predicted a ratio of 1.74: 1, which is close to the observed ratio of 2.07 : 1.

CONCLUSIONS

Application of HIV seroprevalences from pregnant women to whole populations may need adjustment for fertility rates among HIV-infected women. A general method for this has been derived and validated. Gathering fertility data for HIV-infected women is a useful adjunct to serosurveillance.

Age- and sex-specific HIV-1 prevalence in the urban community setting of Addis Ababa, Ethiopia

OBJECTIVE

To estimate the age and sex-specific prevalence of HIV infection in the population of Addis Ababa, Ethiopia.

DESIGN

Two-stage cluster sampling of the population aged 0-49 years of Addis Ababa, using kebeles (urban dwelling associations) as clusters.

METHODS

The sera used for this study were collected in an earlier study (1994) on the rate of acquisition of antibodies against measles, rubella, and hepatitis B. After separate approvals were obtained from the institutional ethics committees, sera were tested by enzyme-linked immunosorbent assay confirmed by Western blot. Age- and sex-specific HIV prevalence rates were estimated. The prevalence of HIV in men and women over 15 years of age was compared by calculating age-standardized HIV prevalence, using the age distribution of the census population as the standard. A time-dependent catalytic model was used to obtain crude estimates of HIV incidence from age-prevalence data.

RESULTS

A total of 3853 sera were available for analysis. The prevalence of HIV in adults was 6.0% [95% confidence interval (CI), 4.5-7.4%] for men and 6.9% (95% CI, 5.3-8.5%) for women, with peak prevalence in the 25-29 year age group of 16.3 and 11.8%, respectively. After standardization for age using the direct method, the HIV prevalence ratio comparing adult men with women was 0.97:1 (95% CI, 0.70:1 - 1.35:1). Three children aged less than 5 years were HIV-positive. The prevalence of HIV among adults ranged from 0-21.3% in different clusters, indicating the heterogeneity of the spread of HIV in the city. HIV prevalence estimates among the antenatal clinic patients of Addis Ababa in 1996 far exceeded the estimates obtained during the community survey, particularly in the youngest age group (15-24 years). Estimates of HIV incidence (per susceptible person per annum) for the age group 16-22 years ranged from 1.3-2.25% for men and from 2.1-2.4% for women.

CONCLUSION

By 1994, a substantial proportion of the adult population of Addis Ababa was infected with HIV. Promotion of behavioural changes and the control of sexually transmitted diseases should be strongly supported to limit the spread of the HIV epidemic in Ethiopia.

Direct estimates of prevalent HIV infection in adults in England and Wales for 1991 and 1993: an improved method

OBJECTIVE

To estimate the number of prevalent HIV infections in England and Wales at the end of 1991 and 1993.

METHOD

A direct method was used whereby population estimates derived from the National Survey of Sexual Attitudes and Lifestyle (NATSAL) and prevalence data from the Unlinked Anonymous HIV Prevalence Monitoring Programme (UAPMP) were combined to produce estimates of the number of adults infected and alive in the population.

RESULTS

In the population of England and Wales the numbers of prevalent infections for defined transmission categories, at the end of 1993, were as follows: 12,600 through sex between men, 2500 through injecting drug use, and 6900 through heterosexual intercourse. The overall estimate was 22,800 HIV seropositive individuals.

CONCLUSIONS

The direct method attempts to provide an estimate of the number of HIV infections using population based survey data. These estimates are consistent with other approaches using independent methods. Such methods are essential for inferring recent HIV incidence, projecting future AIDS cases, and for healthcare planning.