Estimating adult HIV prevalence in the UK in 2003: the direct method of estimation

Knowledge and perceptions of male immigrants in Leeds (UK) towards male circumcision as an HIV prevention strategy

BACKGROUND

The World Health Organization has accepted and recommended medical male circumcision (MMC) as an HIV prevention strategy. Despite the advantages of MMC, the rate of uptake of this practice among immigrants and the general population in the United Kingdom (UK) is low, yet the procedure is provided in public and private health facilities. The role of negative perception and its contribution to low circumcision rates is unknown.

OBJECTIVES

Since immigrants are a key group that is vulnerable to HIV in the UK, this study aimed at understanding their knowledge and perceptions with regard to MMC.

METHODS

We enrolled 10 participants who were purposively selected using snowball recruitment methods. Data were collected during individual in-depth interviews using semi-structured interview guides. Responses were audio recorded, transcribed and analyzed using thematic analysis. Appropriate themes were generated from the data collected.

RESULTS

We found that the majority looked at male circumcision (MC) as a practice to fulfill their cultural and religious obligations rather than as an HIV protection method. Few participants showed belief and certainty that MC or MMC was effective in HIV prevention hence limited knowledge. They also expressed perceived danger. This included fear of pain, complications from the procedure and possible infections when carried out through traditional means. These dangers discouraged study participants from accessing MMC.

CONCLUSION

Male circumcision is mainly practiced to fulfill cultural and religious norms, but is not seen as a credible HIV prevention strategy.

How many people are living with undiagnosed HIV infection? An estimate for Italy, based on surveillance data

Objective:

To estimate the size and characteristics of the undiagnosed HIV population in Italy in 2012 applying a method that does not require surveillance data from the beginning of the HIV epidemic.

Methods:

We adapted the method known as ‘London method 2’; the undiagnosed population is estimated as the ratio between the estimated annual number of simultaneous HIV/clinical AIDS diagnoses and the expected annual progression rate to clinical AIDS in the undiagnosed HIV population; the latter is estimated using the CD4⁺ cell count distribution of asymptomatic patients reported to surveillance. Under-reporting/ascertainment of new diagnoses was also considered. Also, the total number of people living with HIV was estimated.

Results:

The undiagnosed HIV population in 2012 was 13 729 (95% confidence interval: 12 152–15 592), 15 102 (13 366–17 151) and 16 475 (14 581–18 710), assuming no under-reporting/ascertainment, 10 and 20% of under-reporting/ascertainment, respectively. The percentage of undiagnosed cases was higher among HIV people aged below 25 years (25–28%), MSM (16–19%) and people born abroad (16–19%), whereas it was small among injection drug users (3%).

Conclusion:

The estimate of people in Italy with undiagnosed HIV in 2012 was in a plausible range of 12 000–18 000 cases, corresponding to 11–13% of the overall prevalence. The method is straightforward to implement only requiring annual information from the HIV surveillance system about CD4⁺ cell count and clinical stage at HIV diagnosis. Thus, it could be used to monitor if a certain prevention initiative lead to the reduction of the undiagnosed HIV population over time. It can also be easily implemented in other countries collecting the same basic information from the HIV surveillance system.

High rates of late HIV diagnosis among people who inject drugs compared to men who have sex with men and heterosexual men and women in Australia

We aimed to estimate temporal trends in the proportion of HIV diagnoses which could be characterized as recent infections in Australia for men who have sex with men (MSM), people who inject drugs (PWID), and heterosexual men and women using modified back-projection methodology based on data sources from HIV/AIDS Surveillance database. The proportion of HIV diagnoses among MSM that can be classified as recent infections increased in MSM, heterosexual men and women consistently. However, after initial increases during 1996-2000, the proportion of overall recent infections estimated among PWID declined by 50% in 2007 compared to 2000 (from 23 to 11%). These data suggest that late HIV diagnoses were more common among PWID compared to other groups. Ongoing prevention efforts need to be coupled with targeted testing and treatment efforts to increase the diagnosis of recent infection in PWID and reduce apparent inequities in access to screening.

Global epidemiology of HIV infection in men who have sex with men

Epidemics of HIV in men who have sex with men (MSM) continue to expand in most countries. We sought to understand the epidemiological drivers of the global epidemic in MSM and why it continues unabated. We did a comprehensive review of available data for HIV prevalence, incidence, risk factors, and the molecular epidemiology of HIV in MSM from 2007 to 2011, and modelled the dynamics of HIV transmission with an agent-based simulation. Our findings show that the high probability of transmission per act through receptive anal intercourse has a central role in explaining the disproportionate disease burden in MSM. HIV can be transmitted through large MSM networks at great speed. Molecular epidemiological data show substantial clustering of HIV infections in MSM networks, and higher rates of dual-variant and multiple-variant HIV infection in MSM than in heterosexual people in the same populations. Prevention strategies that lower biological transmission and acquisition risks, such as approaches based on antiretrovirals, offer promise for controlling the expanding epidemic in MSM, but their potential effectiveness is limited by structural factors that contribute to low health-seeking behaviours in populations of MSM in many parts of the world.

HIV prevalence among men who have sex with men in New Zealand 1985–2009: 25 years of public health monitoring

Annual population-based estimates of the number of men who have sex with men (MSM) with diagnosed HIV infection (HIV prevalence pool), and the proportion of all MSM this represents (HIV prevalence), have been insufficiently described over the long term. We investigated the dynamic effects of ongoing HIV diagnoses, lower mortality due to treatment and growth in the MSM population over time on these two epidemic indicators using national HIV/AIDS surveillance data in New Zealand, 1985–2009. The diagnosed HIV prevalence pool rose 79% between 1989 and 1999, and 137% between 1999 and 2009. Estimates of diagnosed HIV prevalence as a proportion of MSM were 0.2% of MSM in 1985, and were between 1.5% and 5.0% of MSM by 2009. New Zealand continues to have a relatively low-prevalence HIV epidemic among MSM; however, the number of MSM living with diagnosed infection is growing rapidly 25 years after HIV testing was introduced.

HIV in hiding: methods and data requirements for the estimation of the number of people living with undiagnosed HIV

Many people who are HIV positive are unaware of their infection status. Estimation of the number of people with undiagnosed HIV within a country or region is vital for understanding future need for treatment and for motivating testing programs. We review the available estimation approaches which are in current use. They can be broadly classified into those based on prevalence surveys and those based on reported HIV and AIDS cases. Estimation based on prevalence data requires data from regular prevalence surveys in different population groups together with estimates of the size of these groups. The recommended minimal case reporting data needed to estimate the number of patients with undiagnosed HIV are HIV diagnoses, including CD4 count at diagnosis and whether there has been an AIDS diagnosis in the 3 months before or after HIV diagnosis, and data on deaths in people with HIV. We would encourage all countries to implement several methods that will help develop our understanding of strengths and weaknesses of the various methods.

Estimates of the number of prevalent and incident human immunodeficiency virus (HIV) infections in Canada, 2008

OBJECTIVE

To estimate the number of prevalent and incident HIV infections in Canada in 2008.

METHODS

We applied multiple methods to estimate national HIV prevalence and incidence in Canada, including the workbook method, two statistical modelling methods, and an iterative spreadsheet model.

RESULTS

The estimated number of people living with diagnosed or undiagnosed HIV infection (including AIDS) continues to rise, from an estimated 57,000 in 2005 to 65,000 in 2008. Nearly half (48%) of these HIV-infected persons were men who have sex with men (MSM) and 22% were women. An estimated 16,900 persons with prevalent infection (26% of total prevalent infections) were unaware of their HIV-infected status and this proportion varied from an estimated 19% of HIV-infected MSM, to 25% of HIV-infected people who inject drugs, and 35% of HIV-infected heterosexuals. An estimated 3,300 new infections occurred in Canada in 2008, which was about the same as the estimate of 3200 in 2005. Of those new infections, 26% were among women and 12.5% were of Aboriginal descent; in terms of exposure category, MSM continued to comprise the greatest proportion of new infections (44%) and heterosexuals who originated in countries where HIV is endemic comprised 16%.

CONCLUSION

HIV incidence in Canada is not decreasing. Aboriginal people and people from HIV-endemic countries continue to be over-represented in Canada's HIV epidemic. People unaware of their HIV infection are a priority for being tested and diagnosed to enable them to take advantage of care services and receive counselling to prevent further spread of HIV.

Insights into the rise in HIV infections, 2001 to 2008: a Bayesian synthesis of prevalence evidence

OBJECTIVE

To estimate trends in prevalence of HIV infection, undiagnosed and total, among adults aged 15-44 years in England and Wales since 2001.

DESIGN

Multiple surveillance systems and survey data are available to inform different aspects of the HIV epidemic in England and Wales. To coherently and consistently combine this information to estimate trends in HIV prevalence, we apply a multiparameter evidence synthesis in a Bayesian statistical framework.

METHODS

The study population is stratified by exposure group and region of residence. We synthesize data from behavioural and community surveys, unlinked anonymous seroprevalence surveys, and an annual survey of individuals with diagnosed HIV infection. Prevalence estimates are given with 95% credible intervals.

RESULTS

The estimated number of prevalent HIV infections in 15-44-year-olds has increased from 32,400 (29,600-35,900) in 2001 to 54,500 (50,500-59,100) in 2008, corresponding to an estimated prevalence of 1.5 per 1000 (1.4-1.7) rising to 2.4 per 1000 (2.3-2.6) in 2008. A rise in prevalence of diagnosed infection contributes substantially to the increase. There is no evidence of a statistically significant decrease in the prevalence of undiagnosed infection. The proportion of infections that are diagnosed has therefore also increased.

CONCLUSION

Although the increase in the proportion of infections that are diagnosed is encouraging, the rise in HIV prevalence and lack of evidence of a decrease in prevalence of undiagnosed infection suggest that diagnosis rates are not high enough to reduce the pool of individuals unaware of their infection and that new infections must be occurring.

Multiparameter evidence synthesis in epidemiology and medical decision-making

Meta-analysis has been well-established for many years, but has been largely confined to pooling evidence on pair-wise contrasts. Broader forms of synthesis have also been described, apparently re-invented in disparate fields, each time taking different computational approaches. The potential value of Bayesian estimation of a joint posterior parameter distribution and simultaneously sampling from it for decision analysis has also been appreciated. However, applications have been relatively few in number, sometimes stylized, and presented mainly to a statistical methods audience. As a result, the potential for multiparameter evidence synthesis in both epidemiology and health technology assessment has remained largely unrecognized. The advent of flexible software for Bayesian Markov chain Monte Carlo in the shape of WinBUGS has the made these earlier strands of work more widely available. Researchers can now carry out synthesis at a realistic level of complexity. The Bristol programme has not only contributed to a growing body of literature on how to synthesize different evidence structures, but also on how to check the consistency of multiple information sources and how to use the resulting models to prioritize future research.

HIV in gay and bisexual men in the United Kingdom: 25 years of public health surveillance

It is more than 25 years since the first case of AIDS was reported in the United Kingdom. In December 1981 a gay man was referred to a London hospital with opportunistic infections indicative of immunosuppression. National surveillance began the following year, in September 1982, with the notification of deaths and clinical reports of AIDS and Kaposi's sarcoma plus laboratory reports of opportunistic infections. Since then epidemiological surveillance systems have evolved, adapting to, and taking advantage of advances in treatments and laboratory techniques. The introduction of the HIV antibody test in 1984 led to the reporting of HIV-positive tests by laboratories and the establishment of an unlinked anonymous survey in 1990 measuring undiagnosed HIV infection among gay men attending sexual health clinics. The widespread use of highly active antiretroviral therapies (HAART) since 1996 has averted many deaths among HIV-positive gay men and has also resulted in a large reduction in AIDS cases. This led to a need for an enumeration of gay men with HIV accessing NHS treatment and care services (1995 onwards), more clinical information on HIV diagnoses for epidemiological surveillance (2000 onwards) and the routine monitoring of drug resistance (2001 onwards). Twenty-five years after the first case of AIDS was reported, gay and bisexual men remain the group at greatest risk of acquiring HIV in the United Kingdom. Latest estimates suggest that in 2004, 26 500 gay and bisexual men were living with HIV in the United Kingdom, a quarter of whom were undiagnosed. In this review, we examine how national surveillance systems have evolved over the past 25 years in response to the changing epidemiology of HIV/AIDS among gay and bisexual men in the United Kingdom as well as advances in laboratory techniques and medical treatments. We also reflect on how they will need to continue evolving to effectively inform health policy in the future.

Sexual behaviour and HIV infection in black-Africans in England: results from the Mayisha II survey of sexual attitudes and lifestyles

OBJECTIVES

To estimate HIV prevalence and the distribution of high risk sexual behaviours, sexual health service use, and HIV testing among black Africans aged 16 years or over in England. To determine demographic, behavioural and service use factors associated with HIV prevalence.

METHODS

A cross-sectional community-based survey (Mayisha II) in London, Luton and the West Midlands. A short (24-item) anonymous self-completion questionnaire with linked voluntary anonymous oral fluid sampling, using an Orasure device for HIV testing.

RESULTS

A total of 1359 eligible black African men (51.9%) and women (48.1%) were recruited, of whom 74% (1006) provided a sufficient oral fluid sample for HIV testing. 42.9% of men and 50.9% of women reported ever having had an HIV test. Overall, 14.0% (141, 95% CI 11.9 to 16.3) of respondents tested HIV positive (13.1% of men and 15.0% of women); 9.2% (93) had undiagnosed HIV infection, while 4.8% (48) had a diagnosed HIV infection. HIV prevalence was significantly higher in men: born in East Africa; who had had a previous STI diagnosis; or who were recruited in bars and clubs; and in women: born in East or Southern Africa; aged 25 years and over; who had had two new sexual partners in the past 12 months; or who had had a previous STI diagnosis.

CONCLUSIONS

Despite about half the sample having had an HIV test at some time in the past, 9.2% of respondents had an undiagnosed HIV infection. This study supports current policy efforts to further promote HIV testing and serostatus awareness.

Improving analysis of the size and dynamics of AIDS epidemics

Supplement editors Peter D Ghys and Neff Walker and the Chair of the UNAIDS Reference Group on Estimates, Modelling and Projections, Geoff P Garnett, introduce 13 papers describing the data, methods, and tools used to produce the 2005 UNAIDS/WHO HIV and AIDS estimates