The importance of partnership factors and individual factors associated with absent or inconsistent condom use in heterosexuals: a cross-sectional study.

OBJECTIVES Decisions to use condoms are made within partnerships. We examined the associations between inconsistent or no condom use and individual and partnership characteristics. We also examined the relative importance of individual versus partnership factors. METHODS Cross-sectional study of heterosexual individuals enrolled from the sexually transmitted infections (STI) outpatient clinic in Amsterdam, the Netherlands, from May to August 2010. Participants completed a questionnaire about sexual behaviour with the last four partners in the preceding year. Participant and partnership factors associated with inconsistent or no condom use in steady and casual partnerships were identified. RESULTS 2144 individuals were included, reporting 6401 partnerships; 54.7% were female, the median age was 25 (IQR 22-30) years and 79.9% were Dutch. Inconsistent or no condom use occurred in 13.9% of 2387 steady partnerships and in 33.5% of 4014 casual partnerships. There was statistical evidence of associations between inconsistent condom use in steady partnerships and ethnic concordance, longer duration, higher number of sex acts, practising anal sex, and sex-related drug use. In casual partnerships, associations were found with having an older partner, ethnic concordance, longer duration, higher number of sex acts, anal sex, sex-related drug use, ongoing partnerships and concurrency. In multivariable models, partnership factors explained 50.9% of the variance in steady partnerships and 70.1% in casual partnerships compared with 10.5% and 15.4% respectively for individual factors. CONCLUSIONS Among heterosexual STI clinic attendees in Amsterdam, partnership factors are more important factors related with inconsistent condom use than characteristics of the individual.

Frequency and determinants of unprotected sex among HIV-infected persons: the Swiss HIV cohort study

Access to antiretroviral therapy may have changed condom use behavior. In January 2008, recommendations on condom use for human immunodeficiency virus (HIV)-positive persons were published in Switzerland, which allowed for unprotected sex under well-defined circumstances ("Swiss statement"). We studied the frequency, changes over time, and determinants of unprotected sex among HIV-positive persons.

Investigation of a large community-based outbreak of hepatitis B infection in the United Kingdom

We describe the largest outbreak of hepatitis B virus infection reported to date in the UK. Between July 2001 and December 2005, 237 cases were identified in Avon, South West England. The likely route of transmission was injecting drug use in 44% (104/237) and heterosexual intercourse in 30% (71/237) of cases. A case-control study in injectors showed that injecting crack cocaine [adjusted odds ratio (aOR) 23·8, 95% confidence interval (CI) 3·04-186, P<0·001] and sharing injecting paraphernalia in the year before diagnosis (aOR 16·67, 95% CI 1·78-100, P=0·010) were strongly associated with acute hepatitis B. In non-IDUs number of sexual partners and lack of consistent condom use were high compared to a national sample. We describe the control measures implemented in response to the outbreak. This outbreak has highlighted the problems associated with the low uptake from the national hepatitis B vaccination policy which targets high-risk groups, the difficulties of identifying those at risk of acquiring hepatitis B infection through heterosexual sex, and injecting crack cocaine as a risk factor for hepatitis B.

Unsafe sex and increased incidence of hepatitis C virus infection among HIV-infected men who have sex with men: the Swiss HIV Cohort Study

BACKGROUND: Data on the incidence of hepatitis C virus (HCV) infection among human immunodeficiency virus (HIV)-infected persons are sparse. It is controversial whether and how frequently HCV is transmitted by unprotected sexual intercourse. METHODS: We assessed the HCV seroprevalence and incidence of HCV infection in the Swiss HIV Cohort Study between 1988 and 2004. We investigated the association of HCV seroconversion with mode of HIV acquisition, sex, injection drug use (IDU), and constancy of condom use. Data on condom use or unsafe sexual behavior were prospectively collected between 2000 and 2004. RESULTS: The overall seroprevalence of HCV infection was 33% among a total of 7899 eligible participants and 90% among persons reporting IDU. We observed 104 HCV seroconversions among 3327 participants during a total follow-up time of 16,305 person-years, corresponding to an incidence of 0.64 cases per 100 person-years. The incidence among participants with a history of IDU was 7.4 cases per 100 person-years, compared with 0.23 cases per 100 person-years in patients without such a history (P<.001). In men who had sex with men (MSM) without a history of IDU who reported unsafe sex, the incidence was 0.7 cases per 100 person-years, compared with 0.2 cases per 100 person-years in those not reporting unsafe sex (P=.02), corresponding to an incidence rate ratio of 3.5 (95% confidence interval, 1.2-10.0). The hazard of acquiring HCV infection was elevated among younger participants who were MSM. CONCLUSIONS: HCV infection incidence in the Swiss HIV Cohort Study was mainly associated with IDU. In HIV-infected MSM, HCV infection was associated with unsafe sex.

Sexual transmission of HIV according to viral load and antiretroviral therapy: systematic review and meta-analysis

OBJECTIVES: To synthesize the evidence on the risk of HIV transmission through unprotected sexual intercourse according to viral load and treatment with combination antiretroviral therapy (ART). DESIGN: Systematic review and meta-analysis. METHODS: We searched Medline, Embase and conference abstracts from 1996-2009. We included longitudinal studies of serodiscordant couples reporting on HIV transmission according to plasma viral load or use of ART and used random-effects Poisson regression models to obtain summary transmission rates [with 95% confidence intervals, (CI)]. If there were no transmission events we estimated an upper 97.5% confidence limit. RESULTS: We identified 11 cohorts reporting on 5021 heterosexual couples and 461 HIV-transmission events. The rate of transmission overall from ART-treated patients was 0.46 (95% CI 0.19-1.09) per 100 person-years, based on five events. The transmission rate from a seropositive partner with viral load below 400 copies/ml on ART, based on two studies, was zero with an upper 97.5% confidence limit of 1.27 per 100 person-years, and 0.16 (95% CI 0.02-1.13) per 100 person-years if not on ART, based on five studies and one event. There were insufficient data to calculate rates according to the presence or absence of sexually transmitted infections, condom use, or vaginal or anal intercourse. CONCLUSION: Studies of heterosexual discordant couples observed no transmission in patients treated with ART and with viral load below 400 copies/ml, but data were compatible with one transmission per 79 person-years. Further studies are needed to better define the risk of HIV transmission from patients on ART.

Chlamydia prevalence in young attenders of rural and regional primary care services in Australia: a cross-sectional survey.

OBJECTIVE To estimate chlamydia prevalence among 16-29-year-olds attending general practice clinics in Australia. DESIGN, PARTICIPANTS AND SETTING A cross-sectional survey was conducted from May 2010 to December 2012. Sexually experienced 16-29-year-olds were recruited from 134 general practice clinics in 54 rural and regional towns in four states and in nine metropolitan clinics (consecutive patients were invited to participate). Participants completed a questionnaire and were tested for chlamydia. MAIN OUTCOME MEASURE Chlamydia prevalence. RESULTS Of 4284 participants, 197 tested positive for chlamydia (4.6%; 95% CI, 3.9%-5.3%). Prevalence was similar in men (5.2% [65/1257]; 95% CI, 3.9%-6.4%) and women (4.4% [132/3027]; 95% CI, 3.5%-5.2%) (P = 0.25) and high in those reporting genital symptoms or a partner with a sexually transmissible infection (STI) - 17.0% in men (8/47; 95% CI, 2.8%-31.2%); 9.5% in women (16/169; 95% CI, 5.1%-13.8%). Nearly three-quarters of cases (73.4% [130/177]) were diagnosed in asymptomatic patients attending for non-sexual health reasons, and 83.8% of all participants (3258/3890) had attended for non-sexual health reasons. Prevalence was slightly higher in participants from rural and regional areas (4.8% [179/3724]; 95% CI, 4.0%-5.6%) than those from metropolitan areas (3.1% [17/548]; 95% CI, 1.5%-4.7%) (P = 0.08). In multivariable analysis, increasing partner numbers in previous 12 months (adjusted odds ratio [AOR] for three or more partners, 5.11 [95% CI, 2.35-11.08]), chlamydia diagnosis in previous 12 months (AOR, 4.35 [95% CI, 1.52-12.41]) and inconsistent condom use with most recent partner (AOR, 2.90 [95% CI, 1.31-6.40]) were significantly associated with chlamydia in men. In women, increasing partner numbers in previous 12 months (AOR for two partners, 2.59 [95% CI, 1.59-4.23]; AOR for three or more partners, 3.58 [95% CI, 2.26-5.68]), chlamydia diagnosis in previous 12 months (AOR, 3.13 [95% CI, 1.62-6.06]) and age (AOR for 25-29-year-olds, 0.23 [95% CI, 0.12-0.44]) were associated with chlamydia. CONCLUSIONS Chlamydia prevalence is similar in young men and women attending general practice. Testing only those with genital symptoms or a partner with an STI would have missed three-quarters of cases. Most men and women are amenable to being tested in general practice, even in rural and regional areas.

Hormonal Contraception and the Risk of HIV Acquisition: An Individual Participant Data Meta-analysis.

BACKGROUND Observational studies of a putative association between hormonal contraception (HC) and HIV acquisition have produced conflicting results. We conducted an individual participant data (IPD) meta-analysis of studies from sub-Saharan Africa to compare the incidence of HIV infection in women using combined oral contraceptives (COCs) or the injectable progestins depot-medroxyprogesterone acetate (DMPA) or norethisterone enanthate (NET-EN) with women not using HC. METHODS AND FINDINGS Eligible studies measured HC exposure and incident HIV infection prospectively using standardized measures, enrolled women aged 15-49 y, recorded ≥15 incident HIV infections, and measured prespecified covariates. Our primary analysis estimated the adjusted hazard ratio (aHR) using two-stage random effects meta-analysis, controlling for region, marital status, age, number of sex partners, and condom use. We included 18 studies, including 37,124 women (43,613 woman-years) and 1,830 incident HIV infections. Relative to no HC use, the aHR for HIV acquisition was 1.50 (95% CI 1.24-1.83) for DMPA use, 1.24 (95% CI 0.84-1.82) for NET-EN use, and 1.03 (95% CI 0.88-1.20) for COC use. Between-study heterogeneity was mild (I2 < 50%). DMPA use was associated with increased HIV acquisition compared with COC use (aHR 1.43, 95% CI 1.23-1.67) and NET-EN use (aHR 1.32, 95% CI 1.08-1.61). Effect estimates were attenuated for studies at lower risk of methodological bias (compared with no HC use, aHR for DMPA use 1.22, 95% CI 0.99-1.50; for NET-EN use 0.67, 95% CI 0.47-0.96; and for COC use 0.91, 95% CI 0.73-1.41) compared to those at higher risk of bias (pinteraction = 0.003). Neither age nor herpes simplex virus type 2 infection status modified the HC-HIV relationship. CONCLUSIONS This IPD meta-analysis found no evidence that COC or NET-EN use increases women's risk of HIV but adds to the evidence that DMPA may increase HIV risk, underscoring the need for additional safe and effective contraceptive options for women at high HIV risk. A randomized controlled trial would provide more definitive evidence about the effects of hormonal contraception, particularly DMPA, on HIV risk.

Potential Impact of Sexual Transmission on Ebola Virus Epidemiology: Sierra Leone as a Case Study.

BACKGROUND Sexual transmission of Ebola virus disease (EVD) 6 months after onset of symptoms has been recently documented, and Ebola virus RNA has been detected in semen of survivors up to 9 months after onset of symptoms. As countries affected by the 2013-2015 epidemic in West Africa, by far the largest to date, are declared free of Ebola virus disease (EVD), it remains unclear what threat is posed by rare sexual transmission events that could arise from survivors. METHODOLOGY/PRINCIPAL FINDINGS We devised a compartmental mathematical model that includes sexual transmission from convalescent survivors: a SEICR (susceptible-exposed-infectious-convalescent-recovered) transmission model. We fitted the model to weekly incidence of EVD cases from the 2014-2015 epidemic in Sierra Leone. Sensitivity analyses and Monte Carlo simulations showed that a 0.1% per sex act transmission probability and a 3-month convalescent period (the two key unknown parameters of sexual transmission) create very few additional cases, but would extend the epidemic by 83 days [95% CI: 68-98 days] (p < 0.0001) on average. Strikingly, a 6-month convalescent period extended the average epidemic by 540 days (95% CI: 508-572 days), doubling the current length, despite an insignificant rise in the number of new cases generated. CONCLUSIONS/SIGNIFICANCE Our results show that reductions in the per sex act transmission probability via abstinence and condom use should reduce the number of sporadic sexual transmission events, but will not significantly reduce the epidemic size and may only minimally shorten the length of time the public health community must maintain response preparedness. While the number of infectious survivors is expected to greatly decline over the coming months, our results show that transmission events may still be expected for quite some time as each event results in a new potential cluster of non-sexual transmission. Precise measurement of the convalescent period is thus important for planning ongoing surveillance efforts.