bluuebunny/crossref_metadata_2025 huggingface dataset:
O1-S06.04 Modelling the effectiveness of combination prevention from a house-to-house HIV testing platform in KwaZulu Natal, South Africa
Authors: Alsallaq R , Baeten J , Hughes J , Abu-Raddad L , Celum C , Hallett T
Published: July 2011

Background

Available HIV prevention interventions are partially efficacious, but might offer the best strategy to control HIV through synergistic combination and targeting. Home-based HIV testing and counselling (HBCT), conducted house-to-house, provides rapid population-level knowledge of HIV serostatus and a means to facilitate access to combined HIV prevention interventions: expedited referral to antiretroviral treatment (ART) for HIV+ persons, counselling for behaviour change, promotion of and referral for male circumcision and topical or oral PrEP for high-risk HIV- persons. Thus, massively conducted HBCT could serve as a platform for achieving high coverage of combination HIV prevention (HBCT-plus).

Methods

We used age-sex stratified mathematical model to investigate the impact of HBCT-plus-including population-wide HBCT, behaviour change counselling, initiation of ART for HIV+ persons meeting national guidelines, topical PrEP, and male circumcision-on population-level HIV incidence. Our model was calibrated to data for KwaZulu-Natal province of South Africa. Effects of HBCT and other components of the HBCT-plus intervention package were based on empirical data from African settings.

Results

Without major intervention efforts in this province, the model projects HIV incidence to be approximately 2% through the year 2020. In contrast, with high-coverage of HBCT-plus intervention the model indicates that incidence could be reduced by approximately half, to 1%, under assumptions inAbstract O1-S06.04 table 1. Short and long term reductions in HIV incidence are mediated by short and long term behaviour changes following HBCT, respectively, and are manifested by repeated rounds of HBCT every 4 years. Longer-term impacts are supported by a reduction in infectiousness (due to timely initiation of ART as a result of earlier knowledge of serostatus because of HBCT) and susceptibility (due to circumcision) as well as associated ‘herd immunity’ effects.

Abstract O1-S06.04 Table 1

Uptake assumptions for combination HIV prevention (HBCT-plus)

HBCT intervention HBCT coverage90%Linkage to ART intervention Uptake at CD4=35010% Uptake at CD4=20070% Uptake at CD4=5050%Circumcision intervention Uptake over 4 years50%

Conclusions

Multiple evidence-based HIV preventive interventions combined and delivered through a platform of periodic HBCT could reduce population-level HIV incidence in South Africa by 50% within 4 years. Fast and slow acting components affecting infectiousness and susceptibility can make combination packages particularly strong. Multiple partially-effective tools for HIV prevention can be combined and if coverage is sufficient, substantial reductions in HIV incidence are potentially within reach.
O1-S06.05 Exploring the potential impact on HIV incidence of a reduction in concurrency in rural Uganda: a Modelling Study
Authors: McCreesh N , O'Brien K , Nsubuga R , Shafer L A , Bakker R , Seeley J , Richard W
Published: July 2011

Background

The empirical evidence for an association between sexual partnership concurrency and increased HIV acquisition or transmission is equivocal, and the likely impact of changes in the prevalence of concurrency on HIV incidence in countries with generalised HIV epidemics has not been explored. Despite this, a number of SSA counties have planned or implemented campaigns against concurrency. Evaluation of these campaigns is unlikely to provide strong evidence for the likely impact of changes in concurrency on HIV incidence as it will not be possible to separate the effects of a reduction in concurrency from the effects of a reduction in partnership incidence. This modelling study investigates the potential effect on HIV incidence of an intervention to reduce concurrency in rural Uganda, and in other sub-Saharan Africa populations with higher levels of concurrency.

Methods

Data on the demography, sexual behaviour, and HIV prevalence of a cohort in Masaka, Uganda were used to parameterise an individual-based HIV transmission model. The UNAIDS recommended definition of concurrency was used. Four scenarios with different prevalences of male and female concurrency were modelled. An intervention that reduced partnership concurrency by 50% between 2010 and 2020 (keeping overall partnership incidence constant) was introduced and the impact on HIV incidence in 2020 was calculated.

Results

9.6% (7.9%–11.4%) of men and 0.2% (0.0%–0.4%) of women reported concurrent sexual partnerships in rural Uganda in 2010. Preliminary results suggest that in the model scenario simulating this reported behaviour, the intervention reduces the incidence of HIV by 7.4% in men and 19.9% in women (Abstract O1-S06.05 figure 1, scenario 1a). If more female concurrency is simulated, the potential reductions of the intervention are greater (11.1%–14.8% in men and 21.6%–24.7% in women, Abstract O1-S06.05 figure 1, scenarios 2a and 3a). The potential reductions are also greater when a higher prevalence of male concurrency is simulated (9.7%–15.5% in men and 26.6%–29.6% in women, Abstract O1-S06.05 figure 1, scenarios 1b, 2b and 3b).

Abstract O1-S06.05 Figure 1

The impact of the intervention on HIV incidence in 2020.

Conclusions

In this setting, interventions against concurrency have the potential to reduce the HIV incidence and may have a higher impact on the incidence of HIV in women than in men. However a large simulated change in behaviour resulted in only a moderate decrease in HIV incidence. This study does not provide strong support for the prioritisation of concurrency as a target for behaviour change interventions.
O1-S07.02 Characteristics of women testing positive for rectal STIs using self-collected mailed specimens
Authors: Ladd J , Hsieh Y H , Barnes M , Agreda P , Quinn N , Whittle P , Jett-Goheen M , Hogan T , Gaydos C
Published: July 2011

Background

The websitehttp://www.iwantthekit.org/(IWTK) began offering self-administered rectal swab kits in addition to vaginal swab kits in January 2009 to test forChlamydia trachomatis,Neisseria gonorrhoeae, andTrichomonas vaginalis.

Methods

Swab samples were collected at home by participants and sent by US mail and tested by NAAT (Gen-Probe) assays. Participants submitted separate questionnaires for the vaginal and rectal kits. Data were analysed by STATA, version 11.

Results

In 1084 questionnaires from women submitting vaginal swabs to the IWTK program since 2009, 194 (17.9%) reported anal intercourse (AI) in the last 90 days. Of these women, only 113 (58.2%) also ordered and returned rectal kits for testing. An additional 95 kits were ordered and returned by women who did not report recent AI (82), did not return a vaginal swab (5), or did not answer the AI question on the vaginal questionnaire (8). From a total of 406 rectal kits ordered by women overall, 208 (51.2%) were returned; three had no consent form; thus, 205 were tested. Of those tested, 26 (12.7%) were positive for chlamydia, 5 (2.4%) were positive for gonorrhoea, and 13 (6.3%) were positive for trichomoniasis. Two of these samples were positive for both Chlamydia and gonorrhoea, two for both chlamydia and trichomonas, and one for all three STIs. The total number of women testing positive for any rectal STI was 38 (18.5%), and 35 of these women also received and returned vaginal swabs, 34 of which were tested. Of those tested, 24 (70.5%) were positive for at least one of the three STIs vaginally, indicating that women who tested positive for rectal STIs were at very high risk for vaginal STIs. Of the 38 women with rectal STIs, the median age was 22 yr. and the median age of first rectal sex was 20 yr. Questionnaires demonstrated 93.6% were single, 62.5% were Black, and 21.9% were White. Of the women with rectal STIs, 67.7% reported no symptoms, 12.0% reported no rectal partners in previous yr, 56.0% reported one partner, and 32% reported 2–4 partners. Only 16.0% reported having a new rectal partner in the last 3 months. Half (50.0%) reported never using condoms, 15.4% reported they always used condoms, 15.4% reported using condoms most of the time, and 19.2% reported using condoms some of the time.

Conclusions

Public health officials should be aware that AI and rectal STIs are not uncommon among sexually active women. Future STI screening programs should consider rectal infections.
O1-S07.05 Rare event: rectal specimen collection from males for chlamydial infection in the USA
Authors: Tao G , Hoover K , Body B , Nye M , Kent C
Published: July 2011

Background

US guidelines recommend annual Chlamydia screening of the rectum and urethra among men who have sex with men (MSM) with sexual exposure at these anatomic sites. Routine pharyngeal chlamydia screening is not recommended. About 6% of US males have a history of sex with men. The prevalence of rectal chlamydia has consistently been high among MSM with a history of receptive anal sex. One study indicated that up to 53% of chlamydial infections would be missed and not treated if only urethral testing was performed among MSM. We examined data from a large commercial laboratory corporation with a substantial share of the US market and testing available across all 50 states, that also offers rectal and pharyngeal testing with nucleic acid amplification tests (NAAT), to estimate the frequency and positivity of specimens collected from men by anatomic site for chlamydia testing.

Methods

Data for all Chlamydia testing methods was obtained by a large commercial laboratory between June 2008 and July 2010. The data set was then queried to obtain testing performed on males and analysed for anatomic site, test type, test result and age. Urethral and urine specimens were assumed to be testing for urethral infections.

Results

Chlamydia testing was performed on 227 188 specimens from men: 98.2% urethral, 1.3% rectal, and 0.5% pharyngeal. The age distribution of those tested was: 2.4%<15 years, 15.0% 15–19 years, 15.7% 20–24 years, 15.6% 25–29 years, 12.5% 30–34 years, 10.8% 35–39 years, 10.0% 40–44 years, and 18.0% >44 years. Chlamydia positivity varied by anatomic site (8.7% rectal, 6.9% urethral, and 3.5% pharyngeal), and by age (2.5% <15 years, 13.2% 15–19 years, 12.5% 20–24 years, 7.7% 25–29 years, 5.3% 30–34 years, 3.9% 35–39 years, 3.1% 40–44 years, and 1.7% >44 years). Of 2918 rectal specimens, 17.8% were tested by culture and 75.5% by NAAT, compared to 93.5% of urethral specimens tested by NAAT.

Conclusions

Given the sexual practices of men in the US, it appears that only a small proportion of MSM are appropriately screened for rectal Chlamydia. Lack of FDA clearance for these specimen sources may contribute to the small proportion of MSM being screened for rectal Chlamydia. Interventions to increase rectal chlamydial testing among MSM are needed. Because data from this corporation represents a large proportion of testing in the US, it could be used to monitor changes in chlamydia testing practice among men in the future.
O1-S08.01 High HIV prevalence within a generalised epidemic; condom use, violence, and sexually transmitted infections among female sex workers in Dar es Salaam, Tanzania
Authors: Makyao N , Kangolle A , Gilly A , Somi G , Kazaura M , Kim E , Kibona M , Kamazima S
Published: July 2011

Background

In Tanzania, adult HIV prevalence is estimated at 5.8% and 9.3% in Dar es Salaam, well above the level of a generalised epidemic. Nonetheless, HIV infection and a constellation of associated factors are disproportionately borne by marginalised groups within the country. Female sex workers (FSW) are one such group; however, little is known about them in Tanzania.

Method

Respondent-driven sampling was used to recruit self-identified FSWs aged 15+ years, living in Dar es Salaam, who reported exchanging sexual intercourse for money in the past month. FSWs were interviewed about their social circumstances, STI risk behaviours and tested for HIV, Hepatitis B, C and other STIs. Point estimates and 95% CI were adjusted for social network size and recruitment patterns using RDSAT.

Results

From April to August 2010, 537 FSWs were recruited. Their median age was 29 years (range 15–63). Two FSWs (0.6% 95% CI: 0% to 1.7%) were <10 years when first selling sex (median age 17 years). Condom use at last sex was 82.1% (95% CI: 77.0% to 87.0%), but consistent use varied by type of partner; always condoms use with steady partner was 29.9% (95% CI: 22.8% to 37.6%) and 65.1% (95% CI: 58.4% to 71.4%) with one time client. The major reason for FSWs not using condoms was partner objection (44.1%; 95% CI: 32.6% to 56.2%). The prevalence of STIs and viral hepatitis varied: HIV 30.2% (95% CI: 24.7% to 36.4%); Hepatitis B 5.6 % (95% CI: 3.7% to 8.3%); Hepatitis C 1.4% (95% CI: 0.3% to 3.1%), syphilis 2.1% (95% CI: 0.8% to 3.4%); Gonorrhoea 10% (95% CI: 6.9% to 14.4%), and Chlamydia 6.9% (95% CI: 3.2% to 11.9%). Many (292; 51.7%, 95% CI: 46% to 58%) FSWs had experienced physical violence in the past 12 months and 34.7% (95% CI: 28.7% to 40.6%) had been forced to have sex. Few FSWs were IDU themselves (1.4%; 95% CI: 0.3% to 2.9%), but 5.1% (95% CI: 2.3% to 7.7%) suspected regular clients, and 8.9% (95% CI: 7% to 12%) suspected one-time clients were IDU. These women had significantly higher prevalence of HIV (46.8%; 95% CI: 31.5% to 63.9% compared to 23.1% (95% CI: 16.4% to 29.3%) for FSWs who did not suspect any partner.

Conclusion

FSWs of Dar es Salaam have many-fold higher prevalence of HIV than the general population, with variable levels of other STIs. Their health situation calls for multifaceted services and structural interventions beyond HIV education and condom promotion. Preventive, care and treatment and personal level empowerment strategies are desperately needed among FSWs in Dar es Salaam, Tanzania.
O1-S08.02 Who are the women at risk of HIV infection in rural Zimbabwe and how many are there? Insights into their characteristics, locations, and behaviours
Authors: Elmes J , Nhongo K , Hallett T , White P , Mutsindiri R , Garnett G , Nyamukapa C , Gregson S
Published: July 2011

Background

In Zimbabwe's generalised epidemic, the relative importance of different risk groups to ongoing HIV transmission is unclear. We estimated population sizes and HIV prevalence of women involved in different levels of sex work activity in two socioeconomic locations (rural areas and commercial centres) in east Zimbabwe.

Methods

The baseline survey for a cohort study of 650 women at high risk of HIV infection (WR) was conducted in March 2010, using snowball and location-based methods to recruit women with any form of sexual exchange motivated by material reward including cash-per-act and informal credit-based arrangements. We restricted our analysis to a subset of WR who report receiving money for sex, excluding non-monetary transactions. WR were assigned to high, medium or low activity levels based on, among other factors, the frequency they report receiving money for sex and numbers of partners. CIs are based on Agresti-Coull 95% estimation and p values are for χ2estimation unless otherwise stated.

Results

WR were more common in commercial centres than in rural areas 11.1% (9.9% to 12.4%) vs 5.0% (4.3% to 5.8%). The pattern of sex work activity differed between locations (p=0.049) and mean number of sexual partners, over 2 weeks, in high, medium and low activity WR were 4.1, 1.9 and 1.3 respectively (ANOVA test for trend: p<0.001). High activity WR comprised 2.4% (1.9% to 3.1%) of women in commercial centres vs 0.55% (0.34% to 0.89%) in rural; medium level, 7.1% (6.2% to 8.2%) vs 3.9% (3.3% to 4.7%); and low level, 1.56% (1.13% to 2.13%) vs 0.50% (0.30% to 0.82%),Abstract O1-S08.02 figure 1. Overall, HIV prevalence in WR was higher in commercial centres than in rural areas: 46.5% (95% CI: 38.9% to 54.3%) vs 37.8% (28.4% to 48.1%) (p>0.1). Mean HIV prevalence among high level WR was consistent across socioeconomic strata: 50% (range: 35.8%–64.2%). Prevalence among medium level WR tended to be higher in business centres: 47.5% (38.1% to 57.2%) vs 35.2% (25.1% to 46.8%) in rural areas. In contrast, HIV prevalence in low level WR was higher in rural areas: 44.4% (18.8% to 73.4%) vs 36.4% (19.6% to 57.1%).

Abstract O1-S08.02 Figure 1

Relative size and HIV prevalence of the WR population in two socioeconomic locations in east Zimbabwe. Circle sizes are in proportion to the relative size of WR activity level; the inner ring represents low activity, the central ring high activity and the outer ring medium activity WR.

Conclusions

Sex worker populations may be larger than previously measured in general population surveys in rural Zimbabwe. Given that HIV prevalence among WR is threefold higher than in the general population and the underestimated size of the sex worker population, sex work may be an increasingly important driver of HIV transmission in declining generalised rural African epidemics.
O1-S08.03 Condom use during work time among female sex workers in Benin
Authors: Diabaté S , Chamberland A , Geraldo N , Zannou D M , Loembé M M , Anagonou S , Labbé A C , Tremblay C , Alary M
Published: July 2011

Background

Condom use remains the cornerstone of HIV prevention in sub-Saharan Africa where HIV transmission is predominantly heterosexual. The aim of this study conducted in Cotonou, Benin, was to determine factors associated with unprotected sex among female sex workers (FSW), an important core group for the transmission of HIV and sexually transmitted infections (STI).

Methods

We have recruited and followed 396 FSW in a reference center for STI treatment. Condom use was assessed at enrolment and 6 months thereafter. FSW were asked how often they have used condoms with their clients during the last 7 days of work. During the study, FSW were encouraged to always use condoms with their clients. A generalised estimating equation model for binomial distribution with repeated measures was used to isolate factors independently associated with failure to use condoms during any sexual act.

Results

The cohort comprised 1) 149 HIV-positive FSW, of which 52 were treated with antiretroviral therapy (ART) and 97 were not yet eligible for ART and 2) 247 HIV-negative subjects. Mean age (standard deviation; sd) and mean number of clients (sd) during the last 7 days of work were, respectively, 33.8 (9.3) years and 28.4 (26.1) clients. The majority of the FSW (55.3%) did not practice in brothels or equivalent set ups. At enrolment, 5.6% of the FSW reported that they have never used condoms during the last week of work. The proportion of FSW with full use of condoms during the last 7 days of work increased from 77.8% at enrolment to 90.6% 6 months after. First assessment of condom use (enrolment into the study) [RR 2.17; 95% CI 1.44% to 3.26%], not working in a brothel (RR 2.22; 95% CI 1.39% to 3.54%), having a relatively low monthly income (RR 1.63; 95% CI 1.04% to 2.57%) and older age (RR 1.50; 95% CI 1.03 to 2.21%) were independently associated with failure to always use condoms with the clients. Being HIV-infected or being treated with ART was not associated with the issue of interest. The reasons reported by the FSW for not using condoms during the last sexual act were dominated by the refusal of the client (46.0%).

Conclusion

As suggested by our results, interventions promoting condom use during any commercial sexual act are fruitful and need to target women outside brothels, economically more vulnerable and older FSW as well as their clients.
O1-S08.06 Variability in the numbers and types of sex partners of female sex workers and its impact on HIV prevalence in southern India
Authors: Deering K , Shoveller J , Pickles M , Shaw S , Moses S , Blanchard J , Washington R , Ramesh B M , Isac S , Boily M C
Published: July 2011

Background

Heterogeneity in the structure of sex work within and across female sex worker (FSW) populations may be an important determinant of the spread of HIV. We characterised heterogeneity in sexual structure and assessed how it influenced HIV prevalence on a population level in southern India.

Methods

We used data collected from FSWs and clients in three districts (A, B, C) in Karnataka state, India, as part of the Avahan AIDS Initiative, a large-scale targeted HIV prevention program. A deterministic model of HIV transmission among FSWs/clients was parameterised/fitted to the district (A) with the highest FSW/client HIV prevalence in 2005 (33.9%/6.2%). We conducted multiple sensitivity analyses to examine how sexual structure parameters (Abstract O1-S08.06 figure 1) influenced modelled HIV prevalence within district A and identified sources of heterogeneity that could explain differences in HIV prevalence between district A and districts B and C.

Abstract O1-S08.06 Figure 1

Impact of varying each sexual structure parameter through a wide range (half to double the baseline value) on peak HIV prevalence in district A.1.1Red bars=a positive correlation and grey bars=a negative correlation. Bars are arranged in the order of the absolute impact of each parameter on peak HIV prevalence.

Results

Duration of sex work (2.6-fold), duration of the repeat client/FSW relationship (1.7-fold) and numbers of clients of FSWs (1.6-fold) exhibited the largest differences across districts. In district A, doubling the numbers of clients of FSWs, numbers of visits to FSWs by clients and frequency of sex acts with repeat clients increased HIV prevalence the most. Interestingly, doubling the duration of the repeat FSW-client relationship and fraction of repeat clients decreased HIV prevalence the most (Abstract O1-S08.06 figure 1). The observed differences in the mean numbers of clients per month between districts (A:56; B:46; C:34) could alone explain most of the lower HIV prevalence in districts B and C relative to district A. Relative to that observed in district A, the lower number of sex acts with repeat clients in district B and larger FSW population size in district C could also explain these districts' lower HIV prevalence.

Conclusions

The impact of each sexual structure parameter on HIV prevalence depended on the values of other parameters, since many parameters were correlated to keep the total number of FSW-client/client-FSW partnerships equal. Although the rules defining how parameters need to be empirically validated, results demonstrate how their definition were of critical importance in influencing outcomes. The heterogeneous risk faced by FSWs needs to be recognised to explain differences in HIV prevalence, and to inform population-specific interventions capable of addressing the complexities implied by this heterogeneity.
O1-S09.01 Increased condom use and decreased HIV & STI prevalence among female sex workers following a targeted HIV prevention program in Karnataka, South India
Authors: Moses S , Ramesh B M , Isac S , Reza-Paul S , Alary M , Bradley J , Washington R , Beattie T , Blanchard J
Published: July 2011

Background

We assessed the impact of a large-scale, targeted HIV prevention program among female sex workers (FSWs) in Karnataka state, south India.

Methods

In the context of an HIV prevention program involving 18 districts, funded by the Bill & Melinda Gates Foundation, we conducted initial (R1) and two follow-up (R2 and R3) survey rounds (integrated behavioural and biological assessments), involving random samples of urban FSWs in three selected districts. The total urban FSW population size of the three districts is estimated at 8600. Initial surveys were conducted at 7–19 months following program commencement in 2004–2005, and each follow-up survey at two to three year intervals thereafter. Multivariable logistic regression models were used, with weights to account for a complex sampling design. Results presented are for the three districts combined.

Results

1242 FSWs participated in R1, 1238 in R2 and 1248 in R3. In R3, 98% and 92% of FSWs reported contact by a peer educator and having visited a project STI clinic, respectively. HIV prevalence declined steadily from R1 to R3, and in R3 compared to R1, there were reductions in HIV prevalence (24.8% vs 13.3%, adjusted OR (AOR)=0.59, 95% CI 0.41% to 0.86%, p=0.005); active syphilis (12.7% vs 8.8%, AOR=0.44, 95% CI 0.31% to 0.61%, p<0.001); and high-titre syphilis (6.6% vs 3.2%, AOR=0.33, 95% CI 0.21% to 0.51%, p<0.001). Trichomoniasis (Tv), chlamydial infection (Ct) and gonorrhoea (Ng) were assessed in one district in R3. From R1 to R3, Tv declined from 32.9% to 3.5% (AOR=0.07, 95% CI 0.04% to 0.15%, p<0.001); Ng from 5.4% to 0.9% (AOR 0.22, 95% CI 0.0.07% to 0.71%, p=0.01); and Ct from 10.8% to 4.6% (AOR 0.38, 95% CI 0.19% to 0.75%, p=0.006). Comparing R3 with R1 in all three districts, reported condom use at last sex increased significantly for repeat clients (60.1% to 93.9, AOR 11.2, 95% CI 7.2% to 17.5%, p<0.001); for occasional clients (81.0% to 88.2%, AOR 2.8, 95% CI 1.9% to 4.1%, p<0.001); and for regular (non-commercial) partners (24.4% to 55.9%, AOR 5.0, 95% CI 2.4% to 10.3%, p<0.001). Condom use overall was strongly associated with level of peer educator contact, having been exposed to condom demonstrations, and attendance at a program health clinic.

Conclusions

Over 6 years, this large-scale HIV prevention program for FSWs achieved high rates of program coverage, high rates of condom use with clients, and significant reductions in HIV and STI prevalence. It will be important to sustain these efforts in the long term.
O1-S01.05 Estimating the rate of annual chlamydia screening uptake in US women
Authors: Heijne J , Althaus C , Herzog S , Tao G , Kent C , Low N
Published: July 2011

Background

Annual chlamydia testing of all sexually active women aged 25 years and under followed by a repeated test 3 months after treatment is recommended by the US Centers for Disease Control and Prevention (CDC) guidelines. Data from the Healthcare Effectiveness Data and Information Set (HEDIS) estimate chlamydia test coverage at about 40% per year in the last 5 years. We used empirical data and mathematical models to determine whether observed patterns of chlamydia testing are consistent with CDC guidelines and with actual trends in chlamydia prevalence in US women aged 15–25 years.

Methods

First, published data from women enrolled in commercial health plans from 2002 to 2006 (n=1 985 920) were used to estimate the annual chlamydia testing rate in women aged 15–25. Second, trends in chlamydia prevalence in the same age group were studied using data from 1999/2000 to 2007/2008 (n∼600 each round) from the US National Health and Nutrition Examination Survey (NHANES). We used a Susceptible-Infected-Recovered-Susceptible (SIRS) model to estimate the annual screening rate that fit the chlamydia prevalence data best. The model described a closed population with behavioural parameters reflecting people aged 15–25 years. It explicitly incorporated sexual partnerships and took into account re-infection. Finally, the model was used to examine the effect of repeated chlamydia testing 3 months after treatment on chlamydia prevalence and to calculate repeat infection rates.

Results

The estimated rate at which women are tested for chlamydia ranges from 0.06 to 0.11 per year, which corresponds to a chlamydia test every 9 to 16 years on average and an annual coverage of roughly 10%. We found no statistical evidence that chlamydia prevalence changed between 1999 and 2008 in sexually active women aged 15–25 years taking part in NHANES. Predictions from the model of the impact of screening at a rate of 0.11 per year were consistent with the observed stable chlamydia prevalence. Repeat chlamydia testing 3 months after treatment at the estimated screening level hardly influenced population prevalence. The percentage of women with a repeat infection was highest 3.8 months after treatment.

Conclusion

Our study demonstrates the challenges of implementing chlamydia screening. This study suggests that low rates of chlamydia testing in the US have not reduced population chlamydia prevalence substantially.
O1-S09.02 HIV elimination without antiretroviral therapy (ART) in Southern India: modelling and projected costs
Authors: Pickles M , Vickerman P , Vassall A , Ramesh BM , Deering K , Chandrashekar S , Isac S , Moses S , Alary M , Boily M C
Published: July 2011

Background

There is widespread interest in the use of antiretroviral therapy for eliminating HIV. However, it is possible that bringing other existing interventions to scale, such as condom promotion among female sex workers (FSWs) could reduce HIV transmission to low levels in some settings. Avahan, the Indian AIDS Initiative, has attained high coverage among FSWs in southern India, achieved large increases in condom use (>90% use condoms consistently), and substantial reductions (35–60% relative decreases over 5 years) in FSW HIV prevalence have been observed in the three districts with three rounds of FSW surveys. This modelling analysis projects the long-term impact of the Avahan intervention strategy in these districts.

Methods

A bespoke dynamical model of HIV transmission among FSW/clients was parameterised and fitted to district specific behavioural and STI/HIV prevalence data within a Bayesian framework. The model fits for each district were used to determine whether the long-term impact of the current level of condom use achieved through Avahan, will reduce the HIV incidence among FSWs and clients to less than 1 infection per 1000 FSWs and clients per year (elimination definition used by Granich, Lancet 2009). The probability of local elimination, time till elimination, and costs (extended from detailed costing for first 3 years in 2008 US$) and HIV infections averted of achieving this was estimated.

Results

With the current high level of condom use in all 3 districts, the probability that the HIV incidence among FSWs and clients becoming <1 infection per 1000 by 2050 is >95%. The Abstract O1-S09.02 figure 1 suggests local elimination is likely to occur earlier in Bellary (median: 2023) than in Mysore (2028) and Belgaum (2030), with the required intervention duration being 11–35 years. The discounted cost of achieving local elimination in each of the settings is estimated to be $8-11 000 000 with 5000–11 000 HIV infections averted up to 2050.

Abstract O1-S09.02 Figure 1

Posterior distribution of the year when HIV indicates in FSWs and clients goes below 1 infection per 1000 FSWs and clients.

Conclusion

Our results suggest Avahan could result in local elimination of HIV among FSWs and clients in these districts without ART. Current discussions around the use of ART for HIV elimination should also consider other prevention strategies, especially in concentrated epidemic settings where eliminating HIV from FSWs and clients is likely to eliminate HIV in the general population. Our modest estimated costs for local elimination could be completely offset against averted ART costs.
O1-S09.03 Main results and impact analysis of annual Chlamydia screening in a large register-based programme in the Netherlands
Authors: van den Broek I V F , van Bergen J A N E A M , Fennema H S A , Götz H M , Hoebe C J P A , Over E , van der Sande M A B , Schmid B V , Op de Coul E L M
Published: July 2011

Background

Chlamydia screening programmes can only work when they motivate sufficient persons at risk to get tested regularly. The outcomes of the Chlamydia Screening Implementation (CSI) in the Netherlands are novel and valuable because of the large scale of the programme (315 000 young persons targeted), its systematic nature (invitations based on municipal registers) and its multiple screening rounds (annual invitations in three consecutive years).

Methods

From April 2008 to March 2010, Chlamydia Screening was offered annually to municipal-registered 16–29 year olds in three regions of the Netherlands. A phased implementation was applied by grouping clusters in three random, risk-stratified blocks. Participation and positivity rates were compared between blocks submitted to 1, 2 or 3 screening rounds (3rd round only partially completed). The effect of the repeated screening rounds on the prevalence of Chlamydia in the whole target group was estimated by weighting procedures comparing demographic characteristics of participants and target group.

Results

The participation rate in the first round was 16% among all invitees and 20% among the sexually active target population (M13%, F 25%). The participation fell down to 11% in blocks invited two times and 9% in the block invited three times, whereas it was 13% in the control block invited in round two only. The positivity rate in round one was 4.2% among all participants. Positivity rates decreased significantly to 4.0% in blocks screened twice and to 3.5% in the block screened thrice (p=0.04); in the control block 4.3% tested positive. The population prevalence was estimated at 2.6% in Amsterdam, 3.8% in Rotterdam and 2.4% in South Limburg. The prevalence declined over the three screening rounds, but declines were not significant (see Abstract O1-S09.03 figure 1).

Abstract O1-S09.03 Figure 1

Estimated Chlamydia prevalence among young people invited for Chlamydia screening 1, 2 or 3 times at annual intervals, as compared to a control group invited only once. [*bars indicate high-low estimates for South Limburg, an adaptation to correct for participant selection.

Conclusions

The participation in the CSI project was lower than expected and declined with repeated invitation. Chlamydia positivity rates were reduced by 17% in clusters screened three times, whereas these stayed high in control groups. Only a small and non-significant impact on population prevalence was measured. Further extrapolation of the findings in a simulation model suggest a limited impact on Chlamydia prevalence after 10 years of screening and estimates of cost-effectiveness do not support a nationwide roll-out of this programme in the Netherlands.
O1-S09.04 Modelled impact of changing participation rates on effectiveness of population based chlamydia screening
Authors: Schmid B V , van den Broek I V F , Op de Coul E L M , van Bergen J E A M , Fennema J S A , Götz H M , Hoebe C J P A , Kretzschmar M
Published: July 2011

Background

The Chlamydia Screening Implementation (CSI) is a Dutch large-scale pilot of an internet-based self-sampling Chlamydia trachomatis (Ct) screening program for 16–29-year-old men and women. The effectiveness of CSI can be estimated from changes in the positivity rate of the sampled individuals, but shifts in health-care use and CSI participation rates makes modelling a valuable alternative approach for estimating screening effectiveness.

Methods

We simulated the spread of Ct in a heterosexual population of age 13–65, using sexual survey data to parametrise a dynamic sexual contact network. A screening program was implemented in the model by constructing “participation trees”, which capture the likelihood to participate given an individuals participation history, as observed in the CSI program. Currently available health-care options to test for and treat Ct were also implemented in the model as a baseline (including trends in their usage), against which the effect of screening could be compared. In order to estimate the long-term effects of screening on the Ct prevalence in the Netherlands, future participation rates were estimated from trends in the yearly number of new participants, and by extrapolation of the participation trees.

Results

Compared to a baseline scenario, there is a moderate additional effect of 3 years of screening: the estimated Ct prevalence for the target population (16–29) dropped from 2.8% to 1.7% in large cities, and from 1.9% to 1.2% in more rural regions. As repeated invitees were likely not to participate, the largest effect of screening occurred in its first year when everyone in the target population was invited for the first time. After 3 years, the largest effect of screening on the Ct prevalence had been reached. Due to the anticipated further decrease in participation rates the long-term decrease in Ct prevalence is estimated to be in the range of 0.5–0.7 and 0.4–0.6 per cent-points in urban and rural regions, respectively.

Conclusions

A continued population based screening program has a permanent additional effect on lowering the Ct prevalence in the Netherlands, but the size of this effect is strongly tied to the participation rate in the targeted population. Therefore, the accuracy of long-term predictions of screening effectiveness depends on a good model implementation of the available data on participation behaviour.
O1-S10.02 HIV and bacterial STI testing among men who have sex with men in the USA
Authors: Rosenberger J G , Van Der Pol B , Herbenick D , Novak D S , Reece M , Fortenberry J D
Published: July 2011

Purpose

Growing literature has documented the extent to which bacterial sexually transmitted infections (STI) facilitate transmission/acquisition of HIV. Due to the disproportionate impact of HIV on men who have sex with men (MSM), public health messaging encourages routine STI and HIV screening among this population. This study sought to document testing behaviours among MSM in the US and understand factors associated with STI testing.

Methods

Data were collected via an internet survey from 27 756 18–80 year old MSM members of an online sexual networking website. Measures included sociodemographics, STI/HIV testing behaviours, STI/HIV diagnoses, and lifetime sexual behaviour history.

Results

Participants' mean age was 39.0 years, ethnicities included white (84.5%), Latino (6.4%), African American (3.5%), and most (79.9%) identified as homosexual. Over half (54.2%) indicated they were not in a romantic relationship, and nearly all (88.9%) had been sexually active with more than one partner in the past year. Testing rates (past year) were similar for both HIV(65.4%) and STI (60.8%), yet testing in the past 6 months differed with men reporting more frequent STI testing (63.8%) compared to HIV (46.5%); rates of infection in the previous 2 years included gonorrhoea (4.5%), Chlamydia (4.1%), and HIV (3.2%), with lifetime HIV infection rate being 12.5%. Among men living with HIV infection, rates of bacterial STI testing in the past year were higher (76.1%), with gonorrhoea and Chlamydia rates being 8.6% and 7.6% respectively. Both race and sexual orientation were predictive of bacterial STI testing in the past year, with non-white and bisexual men being less likely to have done so (p<0.01).

Conclusions

These data provide a large scale assessment of HIV and STI testing among MSM in the US Findings from this study highlight gaps in screening between bacterial STI and HIV and suggest a need to promote services that offer HIV and STI testing simultaneously.
O1-S11.05 Adolescent sexual intercourse and neighbourhood social disorder
Authors: Wiehe S , Kwan M P , Hoch S , Brooks B W , Burgess A , Wilson J , Fortenberry J D
Published: July 2011

Background

Little is known about how and where an adolescent lives and spends time relates to her health-related behaviours. Social disorder, or where crime occurs, is associated with various health outcomes but few have considered its association with adolescent sexual behaviour. Our objective was to assess whether contextual exposure to social disorder is correlated with self-reported sexual intercourse among adolescent girls.

Design and Methods

Girls (N=48), aged 14–16, were recruited from a single geographic urban area and monitored for 1 week using a GPS-enabled cell phone. Adolescents completed an ACASI survey on self-reported sexual intercourse in the last 30 days. In addition to recorded home and school address, phones transmitted location data every 5 min (travel points). Using ArcGIS, we defined social disorder as aggregated point-level Unified Crime Report data within a 200 metre Euclidian buffer from home and each travel point. Using Stata, we analysed how social disorder exposures differed among girls who reported having sex or not.

Results

Girls reporting sexual activity spent less time at home (30.9% vs 55.7%, p<0.001) and more time at least 5 km away from home (29.5% vs 12.4%, p=0.01). Girls who reported sex in the last 30 days lived in areas of higher social disorder than girls not reporting sex (p=0.01). There were no significant differences in exposure to social disorder based on travel data among girls reporting sex or not, however. Exposure to social disorder varied by school/non-school day as well as time of day. [Abstract O1-S11.05 figure 1].

Abstract O1-S11.05 Figure 1

Average 200 m crime counts by time of day/day of week and self-reported sexual intercourse in the last 30 days.

Conclusions

Even within neighbourhoods, social disorder surrounding the home as defined by crime within a 1-block radius correlates with adolescent sexual intercourse behaviour. Although adolescents reporting having sex are less likely to spend time at home and more likely to be further from home than girls not reporting sex, the areas where they travel to are not different in terms of social disorder.
O2-S1.02 Is concurrency the new serial monogamy? Evidence from a large survey of people attending contrasting genitourinary medicine (GUM) clinics in England
Authors: Mercer C H , Aicken C R H , Low N , Estcourt C S , White P J , Keane F , Brook G , Rait G , Cassell J A
Published: July 2011

Background

Concurrency is an important risk behaviour for STI transmission at the population level, yet few surveys ask detailed questions about concurrency. Even if partnerships do not overlap, there is potential for STI transmission if the gap between the end of one partnership and the start of the next is short. We examined the prevalence of concurrency, quantified the gap between partners and examined gender differences in a high-risk population.

Methods

Cross-sectional survey of 2203 people attending four contrasting GUM clinics in England in 2009. Attendees completed a questionnaire including questions about their three most recent partnerships in the 3 months prior to attending GUM. Gaps between partners were calculated as the time between most recent sex with a previous partner and first sex with a more recent partner. Partnerships were considered concurrent if the gap was negative.

Results

92% of attendees reported sex partner(s) in the last 3 months, yet, while the median number of partners was 1387 men (48%) and 294 women (28%) reported 2+ partners in this time (p<0.001). For 49% of these attendees, ≥2 of their 3 most recent partners were concurrent (p=0.07 for gender difference). Among the 347 concurrent partnerships reported, the median overlap was long: 113 days (IQR: 28–460 days) with just 40 partnerships (12%) involving an overlap of <2 weeks (no significant gender difference). 40% of attendees with concurrent partners had not used condoms consistently with either partner, and a further 24% of attendees with concurrent partners reported not using condoms at all with either partner. In addition (see Abstract O2-S1.02 figure 1), while 78% of men's partners and 70% of women's were overlapping or had a brief gap (<2 weeks), just 12% and 20% respectively involved a gap between partners of >4 weeks.

Abstract O2-S1.02 Figure 1

Cumulative percentage distribution of the time between partners in the 3 months prior to attending GUM clinic reported by attendees with 2+ partners, by gender.

Conclusions

The majority of GUM attendees reported few partners in the last 3 months, yet half of those with 2+ partners had concurrent partnerships, such that concurrency is as common as serial monogamy in this population. These partnerships typically overlapped by a number of weeks and condoms were seldom used, if at all. Among the serially monogamous, sex with a new partner within days of last sex with a former partner was common so the potential for STI transmission is high. Understanding concurrency and the gaps experienced by high-risk individuals is important for ensuring that health promotion and partner notification are delivered appropriately and effectively.
O2-S1.03 ABC for people with HIV: a longitudinal qualitative study of responses to sexual behaviour recommendations among people receiving antiretroviral therapy in Jinja, Uganda
Authors: Allen C , Mbonye M , Seeley J , Birungi J , Wolff B , Coutinho A , Jaffar S
Published: July 2011

Background

People living with HIV (PLHIV) taking ART are increasingly involved in positive prevention" initiatives. These are generally oriented to promoting Abstinence, “Being faithful” (partner reduction) and condom use.

Methods

We conducted a longitudinal qualitative study with PLHIV using ART, who were provided with adherence education and counselling support by a Ugandan non-governmental organisation, The AIDS Service Organisation (TASO). Participants were 40 people selected sequentially as they started ART, stratified by sex, ART delivery mode (clinic- or home-based), and HIV progression stage (early or advanced). At enrolment and 3, 6, 18 and 30 months, semi-structured interviews and home observation visits explored adherence and life changes.

Results

At initiation of ART, participants agreed to follow TASO's positive-living (similar to ABC) recommendations. Initially poor health prevented sexual activity. As health improved, participants prioritised resuming economic production and support for their children. With further improvements, sexual desire resurfaced and people in relationships cemented these via sex. Married male participants were able to use condoms with their wives, but married female participants were unable to assure consistent condom use despite serostatus disclosure to their husbands. Several participants sought and some obtained HIV positive partners (serosorting) for emotional security, support in ART adherence, sexual fulfilment, avoidance of stigma and sometimes parenthood. Respondents used condoms in the early period of new relationships, but several did not disclose HIV status to partners at first. Male partners of female respondents stopped using condoms after a variable initial period. This contributed to continued non-disclosure, since the women feared violence or loss of economic security from disclosure.

Conclusion

Positive prevention interventions continue to concentrate on behavioural outcomes and education and counselling approaches. Our findings show that, as ART leads to health improvements, gender norms, economic needs, sexual desires and a wish for “normalisation” of social roles and relationships increasingly influence sexual behaviour. Positive Health, Dignity and Prevention require combinations of appropriate biological, behavioural and structural interventions tailored to the economic and cultural milieu and informed by an appreciation of the human rights of PLHIV.