Risky sexual behaviour in context: qualitative results from an investigation into risk factors for seroconversion among gay men who test for HIV.

OBJECTIVES: The INSIGHT case-control study confirmed that HIV serodiscordant unprotected anal intercourse (SdUAI) remains the primary risk factor for HIV infection in gay men in England. This paper uses qualitative follow-up data to examine the contexts of SdUAI and other risk factors among the case-control study participants. METHODS: In-depth interviews were conducted with 26 recent HIV seroconverters and 22 non-converters. Purposive selection was used to provide diversity in demographics and sexual behaviour and to facilitate exploration of risk factors identified in the case-control study. RESULTS: Condoms were perceived as barriers to intimacy, trust and spontaneity. The potential consequences of the loss of these were traded off against the consequences of HIV infection. Previous negative HIV tests and the adoption of risk reduction strategies diminished the perceived threat of HIV infection, supporting beliefs that HIV was something that happened to others. Depression and low self-esteem, often combined with use of alcohol or other drugs, led to further risk taking and loss of control over risk reduction strategies. CONCLUSIONS: A range of psychosocial reasons led some men to engage in UAI with serodiscordant or unknown partners, despite high levels of risk awareness. Men in their mid-life, those in serodiscordant relationships and men that had experienced bereavement or other significant, negative, life events revealed factors related to these circumstances that contributed to increases in risky UAI. A diverse portfolio of interventions is required to build confidence and control over safer sex practices that are responsive to gay men's wider emotional needs.

Could male circumcision reduce HIV incidence in the UK?

We consider the public health relevance of three recent African clinical trials showing male circumcision (MC) to reduce female-to-male transmission of HIV for the UK. Although heterosexually acquired HIV infections now account for the majority of new diagnoses in the UK each year, it is important to note that when considering the public health relevance of MC for the UK a large majority of these infections are acquired abroad. Men who have sex with men (MSM) remain those most at risk of acquiring their HIV infection in the UK. The efficacy and effectiveness of MC among MSM and in particular its protective role in unprotected anal intercourse between men remains unknown. Any future consideration of the role of MC in reducing HIV incidence in the UK should not be at the expense of weakening existing effective interventions.

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.

Factors associated with HIV seroconversion in gay men in England at the start of the 21st century.

OBJECTIVES: To detect and quantify current risk factors for HIV seroconversion among gay men seeking repeat tests at sexual health clinics. DESIGN: Unmatched case control study conducted in London, Brighton and Manchester, UK. METHODS: 75 cases (recent HIV positive test following a negative test within the past 2 years) and 157 controls (recent HIV negative test following a previous negative test within the past 2 years) completed a computer-assisted self interview focused on sexual behaviour and lifestyle between HIV tests. RESULTS: Cases and controls were similar in socio-demographics, years since commencing sex with men, lifetime number of HIV tests, reasons for seeking their previous HIV tests and the interval between last HIV tests (mean = 10.5 months). Risk factors between tests included unprotected receptive anal intercourse (URAI) with partners not believed to be HIV negative (adjusted odds ratio (AOR) and 95% confidence interval 4.1, 1.8 to 9.3), where increased risk was associated with concomitant use of nitrite inhalants, receiving ejaculate and increasing numbers of partners. Independent risk was also detected for unprotected insertive anal intercourse (UIAI) with more than one man (AOR 2.7, 1.3 to 5.5) and use of nitrite inhalants (AOR 2.4, 1.1 to 5.2). CONCLUSIONS: HIV serodiscordant unprotected anal intercourse remains the primary context for HIV transmission among gay men, with increased risk associated with being the receptive partner, receiving ejaculate and use of nitrite inhalants. Although the HIV transmission risk of URAI is widely acknowledged, this study highlights the risk of UIAI and that nitrite inhalants may be an important facilitator of transmission when HIV exposure occurs.

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

BACKGROUND: Estimates of the total number of prevalent HIV infections attributable to the major routes of infection make an important contribution to public health policy, as they are used for planning services. METHODS: In the UK, estimates were derived through the "direct method" which estimated the total number of diagnosed and undiagnosed HIV infections in the population. The direct method has been improved over a number of years since first used in 1994, as further data became available such as the inclusion of newly available behavioural survey data both from the National Survey of Sexual Attitudes and Lifestyles (Natsal 2000) and community surveys of men who have sex with men (MSM). These data were used to re-estimate numbers of people unaware of their infection and provided ethnic breakdowns within behavioural categories. The total population was divided into 10 mutually exclusive behavioural categories relevant to HIV risk in the UK-for example, MSM and injecting drug users. Estimates of the population size within each group were derived from Natsal 2000 and National Statistics mid-year population estimates. The total number of undiagnosed HIV infections was calculated by multiplying the undiagnosed HIV prevalence for each group, derived from the Unlinked Anonymous HIV Prevalence Monitoring Programme surveys (UAPMP), by the population size. These estimates were then added to the prevalent diagnosed HIV infections within each group derived from the national census of diagnosed HIV infections, the Survey of Prevalent HIV Infections Diagnosed (SOPHID). The estimates were then adjusted to include all adults in the UK. Because undiagnosed HIV prevalence estimates were not available for each of the behavioural categories, the UAPMP prevalence estimates were adjusted using available data to provide the best estimates for each group. RESULTS: It is estimated that 53,000 individuals are infected with HIV in the UK in 2003, of whom 27% were unaware of their infection. Of the total of 53,000, an estimated 26,000 were among heterosexually infected and 24,500 among MSM. CONCLUSION: The direct method uses an explicit framework and data from different components of the HIV surveillance system to estimate HIV prevalence in the UK, allowing for a comprehensive picture of the epidemic.

Factors associated with heterosexual transmission of HIV to individuals without a major risk within England, Wales, and Northern Ireland: a comparison with national probability surveys.

OBJECTIVE: To compare the prevalence of HIV risk behaviours reported by heterosexuals without major risks for HIV acquisition diagnosed with HIV in England, Wales, and Northern Ireland, with those of the heterosexual general population. METHODS: Demographic and sexual behaviour data for heterosexuals (without major risks for HIV) aged 16-44 from the British National Surveys of Sexual Attitudes and Lifestyles in 1990 and 2000 were compared to 139 HIV infected individuals without major risks for HIV aged 16+ at diagnosis, interviewed between December 1987 and March 2003. Comparisons were made overall and separately for the early and late 1990s. RESULTS: HIV infected heterosexual men without major risks were significantly more likely to report first heterosexual intercourse before age 16 (adjusted odds ratio (AOR): 2.75; 95% confidence interval (CI),1.65 to 4.57), while both HIV infected heterosexual men and women reported greater partner numbers (AOR: men 2.44; CI, 1.4 to 4.05; AOR women 2.17; CI, 1.28 to 3.66) and never using condoms (AOR: men 7.97; CI,4.78 to 13.3; AOR women 3.95; CI, 2.30 to 6.80) than the heterosexual general population. There is evidence to suggest that the two groups were more similar in their reporting of partner numbers in the late 1990s relative to the early 1990s. CONCLUSION: Heterosexual HIV infected individuals without major risks for HIV acquisition in England, Wales, and Northern Ireland are significantly more likely to report high risk sexual behaviours relative to the British heterosexual general population. However, these differences may have decreased over time, at least for the number of partners. Effective sexual health promotion, including the continued promotion of condom use, would impact on the rising rates of STI diagnoses and also prevent HIV transmission among the heterosexual general population.

Late diagnosis of HIV infection among individuals with low, unrecognised or unacknowledged risks in England, Wales and Northern Ireland.

A small number of UK nationals who have a low, unrecognised or unacknowledged risk for HIV present late in the course of HIV infection; often after frequent attendances to primary care physicians. Information from in-depth interviews with individuals diagnosed with HIV in England, Wales and Northern Ireland (EW&NI) was analysed. Those diagnosed because of HIV-related symptoms (late diagnoses) were compared with those diagnosed for other reasons. Of the 286 individuals interviewed, 157 (55%) had HIV-related symptoms at the time of diagnosis, and 129 were tested for other reasons. A greater proportion of those diagnosed late were male and older. Of the 157 late diagnoses, 77 were considered to have acquired HIV heterosexually in the UK, 19 heterosexually abroad, 16 through 'high-risk' behaviours, 15 heterosexually by a 'high-risk' partner, four through blood transfusion and the remainder through an unusual or unknown route. A significantly higher proportion of those diagnosed late had had a long-standing relationship. None had been informed by a current or ex-partner of their HIV status. Primary care physicians should consider HIV as a possibility when patients without an apparent risk for HIV-infection present with symptoms indicative of possible immune suppression. Sensitive partner notification practices that enable a greater number of individuals to inform their partners should be explored.

Management of blinding disease: loss of immunity and superinfection.

Globally the most important loss of immunity currently occurs with HIV disease. The effects of HIV on the eye, since the advent of highly active antiretroviral therapy, have been less in countries where such treatment is available but even in such situations ophthalmic zoster can occur at higher CD4 cell counts and can still cause problems. Other opportunistic infections such as CMV retinitis tend to occur at lower CD4 cell counts. However, globally treatment is not universally available in resource poor countries where it is most needed. A major impact of HIV in such situations is on premature mortality affecting the health care and education workforce, which indirectly has an impact on blinding disease. In addition, loss of family income due to illness or death of parents can affect nutritional status of remaining family members especially children as well as the direct effect of opportunistic infections in the eyes of those infected with HIV.

Men who have sex with men who are born abroad and diagnosed with HIV in England and Wales: an epidemiological perspective.

Relatively little is known about the sexual health needs of men who have sex with men (MSM) born abroad who reside in the UK. We describe here the epidemiology of HIV among MSM born outside the UK and diagnosed with HIV in England and Wales. Reports of HIV diagnoses in England and Wales received at the Health Protection Agency Centre for Infections were analysed. Between 2000 and 2003, 6386 MSM were diagnosed with HIV in England and Wales. Country of birth was recorded for 3571 (56%). Of those with country of birth reported, 2598 (73%) were born in the UK and 973 (27%) abroad. Of those born abroad (973), 424 (44%) were born in Europe, 141 (15%) in Africa, 104 (11%) in South/Central America and the remainder in other regions. Where reported (949), 69% of MSM born abroad were White, 12% other/mixed, 9% Black Caribbean and 7% Black African. Probable country of infection was reported for 612 MSM born abroad: 52% were infected in the UK, 43% in their region of birth and 5% in another region. Men born abroad represent a significant proportion of HIV diagnoses among MSM in England and Wales. More than half probably acquired their HIV infection in the UK, strengthening the call for targeted HIV prevention and sexual health promotion among MSM who are not born in England and Wales.

Epidemiology of HIV among black and minority ethnic men who have sex with men in England and Wales.

OBJECTIVES: To examine the epidemiology of HIV among black and minority ethnic (BME) men who have sex with men (MSM) in England and Wales (E&W). METHODS: Ethnicity data from two national HIV/AIDS surveillance systems were reviewed (1997-2002 inclusive), providing information on new HIV diagnoses and those accessing NHS HIV treatment and care services. In addition, undiagnosed HIV prevalence among MSM attending 14 genitourinary medicine (GUM) clinics participating in the Unlinked Anonymous Prevalence Monitoring Programme and having routine syphilis serology was examined by world region of birth. RESULTS: Between 1997 and 2002, 1040 BME MSM were newly diagnosed with HIV in E&W, representing 12% of all new diagnoses reported among MSM. Of the 1040 BME MSM, 27% were black Caribbean, 12% black African, 10% black other, 8% Indian/Pakistani/Bangladeshi, and 44% other/mixed. Where reported (n = 395), 58% of BME MSM were probably infected in the United Kingdom. An estimated 7.4% (approximate 95% CI: 4.4% to 12.5%) of BME MSM aged 16-44 in E&W were living with diagnosed HIV in 2002 compared with 3.2% (approximate 95% CI: 2.6% to 3.9%) of white MSM (p<0.001). Of Caribbean born MSM attending GUM clinics between 1997 and 2002, the proportion with undiagnosed HIV infection was 15.8% (95% CI: 11.7% to 20.8%), while among MSM born in other regions it remained below 6.0%. CONCLUSIONS: Between 1997-2002, BME MSM accounted for just over one in 10 new HIV diagnoses among MSM in E & W; more than half probably acquired their infection in the United Kingdom. In 2002, the proportion of BME MSM living with diagnosed HIV in E&W was significantly higher than white MSM. Undiagnosed HIV prevalence in Caribbean born MSM was high. These data confirm the need to remain alert to the sexual health needs and evolving epidemiology of HIV among BME MSM in E&W.

The changing epidemiology of prevalent diagnosed HIV infections in England, Wales, and Northern Ireland, 1997 to 2003.

OBJECTIVES: To present the current epidemiology of prevalent diagnosed HIV infections in England, Wales, and Northern Ireland (E, W, & NI) and describe trends over time. METHODS: Descriptive analyses of the annual national Survey of Prevalent HIV Infections Diagnosed (SOPHID) for the period 1997 to 2003. RESULTS: In 2003, 34 251 adults (15 years of age or over) were seen for HIV related care in E, W, & NI, representing a 17% increase in the prevalence of diagnosed HIV infections compared with 2002 and a 132% increase compared with 1997. Between 1997 and 2003, as a proportion of total prevalent cases, adults who acquired their infection through heterosexual sex increased from 26% to 49%; black African adults increased from 15% to 35% and diagnosed adults resident in London fell from 62% to 55% of the total. The male to female ratio declined from 5:1 to 2:1. The proportion of adults receiving combination antiretroviral therapy increased from 53% in 1998 to 64% in 2003. CONCLUSION: There has been a large increase in the number of adults with diagnosed HIV infection seen for care in E, W, & NI since 1997. Changes in the epidemiology of prevalent diagnosed HIV were seen by sex, route of infection, ethnicity, level of antiretroviral therapy, and areas of residence and treatment. In 2003, for the first time, prevalent diagnosed infections acquired through heterosexual sex over-took those acquired through sex between men. These increases have serious implications for the planning and financing of HIV services in the United Kingdom.

The risk of cancer in HIV-infected people in southeast England: a cohort study.

This study used data from the Communicable Disease Surveillance Centre's national HIV database and the Thames Cancer Registry to assess the risk of cancer in HIV-infected people in southeast England. Among 26 080 HIV-infected men with 158,660 person-years follow-up, 1851 cancers, and among 7110 HIV-infected women (31 098 person-years), 171 cancers were identified. The standardised incidence ratio (SIR) for all non-AIDS-defining cancers was significantly increased in HIV-infected men (2.8, 95% confidence interval (CI) 2.6-3.1) but was nonsignificant in HIV-infected women (1.1, 95% CI 0.8-1.6). Most of the cancers observed were in men (n = 1559) and women (n = 127) with AIDS, and among them, the SIR for all non-AIDS-defining cancers was significantly increased in men (8.2, 95% CI 7.2-9.2) and women (2.8, 95% CI 1.6-4.6). The SIR for all non-AIDS-defining cancers was only just significantly increased in men with HIV-infection but not AIDS (1.2, 95% CI 1.0-1.5) and was nonsignificant in such women (0.8, 95% CI 0.5-1.2).

Recent trends in diagnoses of HIV and other sexually transmitted infections in England and Wales among men who have sex with men.

OBJECTIVES: To examine trends in rates of diagnoses of HIV and other sexually transmitted infections (STIs) in men who have sex with men (MSM) in England and Wales between 1997 and 2002. METHODS: Estimates of the MSM population living in England and Wales, London and the rest of England and Wales were applied to surveillance data, providing rates of diagnoses of HIV and STIs and age group specific rates for HIV and uncomplicated gonorrhoea. RESULTS: Between 1997 and 2002, rates of diagnoses of HIV and acute STIs in MSM increased substantially. Rates in London were higher than elsewhere. Rises in acute STIs were similar throughout England and Wales, except for uncomplicated gonorrhoea and infectious syphilis, with greater increases outside London. Rates of gonorrhoea diagnoses doubled between 1999 and 2001 (661/100,000, 1271/100,000, p<0.001) in England and Wales followed by a slight decline to 1210/100,000 (p=0.03) in 2002-primarily the result of a decline in diagnoses among men aged 25-34 (1340/100,000, 1128/100,000, p<0.001) and 35-44 (924/100,000, 863/100,000, p=0.03) in London. HIV was the third most common STI diagnosed in MSM in England and Wales and the second in London, with the highest rate (1286/100,000) found among men aged 35-44 in London in 2002. CONCLUSIONS: Rates of diagnosis of HIV and other STIs have increased substantially among MSM in England and Wales. Increases show heterogeneity by infection, geography, and age over time. Rates in London were twice those seen elsewhere, with greatest changes over time. The observed changes reflect concomitant increases in high risk behaviour documented in behavioural surveillance survey programmes.

HTLV infection in England and Wales in 2002--results from an enhanced national surveillance system.

Human T-cell lymphotropic virus (HTLV) is a retrovirus transmitted through breastfeeding, sexual contact, blood transfusion and injecting drug use. HTLV is endemic in the Caribbean and parts of Africa, Japan and South America, with isolated foci in other areas. Infection is life-long. Less than 5% of those infected progress to one of the HTLV-related diseases, but these are debilitating and often fatal. Laboratory reports of new HTLV diagnoses are followed up through clinicians to establish information such as probable country of infection, country of birth, clinical details and reason for test. Clinician reports are also received for HTLV-infected blood donors identified by the National Blood Service. Seventy-seven individuals newly diagnosed with HTLV infection in 2002 were reported to the Communicable Disease Surveillance Centre (CDSC) by June 2003. Thirty-three (43%) were male, and 44 (57%) female, with median ages at diagnosis of 58.5 and 50.1 years respectively. Seventy-three (95%) individuals were HTLV-I positive and three HTLV-II positive, with one remaining untyped. For 52 of the 77 infections, clinician reports were received. Where ethnicity was reported (48), 30 (63%) were Black Caribbean, 12 (25%) White, and the remainder (6) of other ethnicities. Probable route of infection was reported for 31 individuals: nine (29%) were probably infected heterosexually, seven (23%) through mother-to-child transmission, 12 (40%) through either route, two through blood transfusion, and one through injecting drug use (HTLV-II positive). Where probable country of infection was reported (31), 14 (45%) were probably infected in the UK, 13 (42%) in the Caribbean, and four elsewhere. Where reported (50), reason for test was: symptoms for 19 (38%) individuals, blood donation for 21 (42%), and the remainder for other reasons. Numbers of new HTLV diagnoses were relatively high in 2002, and the characteristics of patients and clinical presentations differed from previous years, mainly due to the introduction of blood donor testing for anti-HTLV. Beyond 2004, the number of HTLV-infected individuals detected through blood donation is expected to decline. While numbers of individuals affected are small compared to many other diseases, the infection is chronic and untreatable, and it is important that adequate standards of diagnosis, prevention, care and support are provided, and surveillance maintained.

Recent trends in HIV and other STIs in the United Kingdom: data to the end of 2002.

Sexual health in the United Kingdom has deteriorated in recent years with further increases in HIV and other sexually transmitted infections (STIs) reported in 2002. This paper describes results from the available surveillance data in the United Kingdom from the Health Protection Agency and its national collaborators. The data sources range from voluntary reports of HIV/AIDS from clinicians, CD4 cell count monitoring, a national census of individuals living with HIV, and the Unlinked Anonymous Programme, to statutory reports of STIs from genitourinary medicine (GUM) clinics and enhanced STI surveillance systems. In 2002, an estimated 49500 adults aged over 15 years were living with HIV in the United Kingdom, of whom 31% were unaware of their infection. Diagnoses of new HIV infections have doubled from 1997 to 2002, mainly driven by heterosexuals who acquired their infection abroad. HIV transmission also continues within the United Kingdom, particularly among homo/bisexual men who, in 2002, accounted for 80% of all newly diagnosed HIV infections acquired in the United Kingdom. New diagnoses of syphilis have increased eightfold, and diagnoses of chlamydia and gonorrhoea have doubled from 1997 to 2002 overall; STI rates disproportionately affect homo/bisexual men and young people. Effective surveillance is essential in the provision of timely information on the changing epidemiology of HIV and other STIs; this information is necessary for the targeting of prevention efforts and through providing baseline information against which progress towards targets can be monitored.

Epidemiology of HIV in young people in England, Wales and Northern Ireland.

We describe the epidemiology of HIV among young people (15-24 years) in England, Wales and Northern Ireland (E, W&NI) between 1997 and 2001 inclusive. Rising rates of sexually transmitted infections (STIs) and 'risk' behaviours suggest that they are at increased risk of acquiring HIV. Data from three national surveillance systems are reviewed. Over the period, 1,624 young people were diagnosed with HIV (10% of all new diagnoses). In 1997 there were 254 new diagnoses, rising to 493 in 2001, a 1.9-fold increase. Of the total, 890 (55%) were heterosexually infected (81% female), 631 through sex between men, and the remainder via other routes. Where probable country of infection was reported (1,139), 618 (54%) were infected in Africa and 362 (32%) in the UK. In 1997, 675 young people accessed HIV-related services, rising to 975 in 2001: an increase of 1.4 fold. In 2001, for 34 of those accessing services the likely route of infection was perinatal. Between 1997 and 2001 inclusive, HIV prevalence among young heterosexual genitourinary medicine (GUM) clinic attendees was 0.17% (193/116,443), and for young homo/bisexual males, 3.4% (174/5,086). Sixty-five percent (104/159) of previously undiagnosed HIV-infected heterosexuals and 47% (51/108) of previously undiagnosed HIV-infected homo/bisexual males left the clinic unaware of their infection. In 2000 and 2001, overall prevalence was 0.11% (77/70,455) among young women giving birth. HIV diagnoses in young people have increased in recent years, while HIV prevalence among young people attending GUM clinics and giving birth has remained low. However, with dramatic increases in chlamydia rates among young women over the past decade, and the highest rates of gonorrhoea and concurrent partnerships among young people, concern about the potential for HIV transmission remains.

Black Caribbean adults with HIV in England, Wales, and Northern Ireland: an emerging epidemic?

BACKGROUND: HIV is now well established in the Caribbean, with prevalence in several countries being surpassed only by those of sub-Saharan Africa. Continuing inward migration from the Caribbean and a high incidence of some bacterial STIs among Britain's black Caribbean communities, suggests a considerable potential for HIV spread. METHODS: Data from three national HIV/AIDS surveillance systems were reviewed, providing information on new HIV diagnoses, numbers accessing treatment and care services, and HIV prevalence. RESULTS: Between 1997 and 2001, 528 black Caribbean adults were newly diagnosed with HIV; 62 new diagnoses in 1997, rising to 176 in 2001. Probable heterosexual acquisition accounted for 335 (63%) infections (161 (48%) males, 174 females), and sex between men 171 (32%). Infection was acquired both in the Caribbean and in the United Kingdom. Numbers of black Caribbeans accessing treatment and care services more than doubled between 1997 (294) and 2001 (691). In 2001, 528 (76%) black Caribbeans accessing services were London residents. Among the Caribbean born previously undiagnosed heterosexuals, HIV prevalence was 0.7%; among men who have sex with men (MSM) it was 10.4%. Of those born in the Caribbean, 73% of male heterosexuals, 50% of female heterosexuals, and 65% of MSM who were previously undiagnosed left the clinic unaware of their HIV infection. CONCLUSIONS: Numbers of black Caribbean adults newly diagnosed and accessing treatment and care services in England, Wales, and Northern Ireland increased between 1997 and 2001. Despite a high prevalence of diagnosed bacterial STIs, prevalence among Caribbean born heterosexuals remains low, but it is high among MSM. Surveillance data highlight the need for targeted HIV prevention among black Caribbeans.

Nitrogen fixation in the activated sludge treatment of thermomechanical pulping wastewater: effect of dissolved oxygen.

N-ViroTech, a novel technology which selects for nitrogen-fixing bacteria as the bacteria primarily responsible for carbon removal, has been developed to treat nutrient limited wastewaters to a high quality without the addition of nitrogen, and only minimal addition of phosphorus. Selection of the operating dissolved oxygen level to maximise nitrogen fixation forms a key component of the technology. Pilot scale activated sludge treatment of a thermomechanical pulping wastewater was carried out in nitrogen-fixing mode over a 15 month period. The effect of dissolved oxygen was studied at three levels: 14% (Phase 1), 5% (Phase 2) and 30% (Phase 3). The plant was operated at an organic loading of 0.7-1.1 kg BOD5/m3/d, a solids retention time of approximately 10 d, a hydraulic retention time of 1.4 d and a F:M ratio of 0.17-0.23 mg BOD5/mg VSS/d. Treatment performance was very stable over the three dissolved oxygen operating levels. The plant achieved 94-96% BOD removal, 82-87% total COD removal, 79-87% soluble COD removal, and >99% total extractives removal. The lowest organic carbon removals were observed during operation at 30% DO but were more likely to be due to phosphorus limitation than operation at high dissolved oxygen, as there was a significant decrease in phosphorus entering the plant during Phase 3. Discharge of dissolved nitrogen, ammonium and oxidised nitrogen were consistently low (1.1-1.6 mg/L DKN, 0.1-0.2 mg/L NH4+-N and 0.0 mg/L oxidised nitrogen). Discharge of dissolved phosphorus was 2.8 mg/L, 0.1 mg/L and 0.6 mg/L DRP in Phases 1, 2 and 3 respectively. It was postulated that a population of polyphosphate accumulating bacteria developed during Phase 1. Operation at low dissolved oxygen during Phase 2 appeared to promote biological phosphorus uptake which may have been affected by raising the dissolved oxygen to 30% in Phase 3. Total nitrogen and phosphorus discharge was dependent on efficient secondary clarification, and improved over the course of the study as suspended solids discharge improved. Nitrogen fixation was demonstrated throughout the study using an acetylene reduction assay. Based on nitrogen balances around the plant, there was a 55, 354 and 98% increase in nitrogen during Phases 1, 2 and 3 respectively. There was a significant decrease in phosphorus between Phases 1 and 2, and Phase 3 of the study, as well as a significant increase in nitrogen between Phases 2 and 3 which masked the effect of changing the dissolved oxygen. Operation at low dissolved oxygen appeared to confer a competitive advantage to the nitrogen-fixing bacteria.