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.

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.

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.

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.

Pre-AIDS mortality in HIV-infected individuals in England, Wales and Northern Ireland, 1982-1996.

OBJECTIVE: To assess pre-AIDS mortality in HIV-infected patients in England, Wales and Northern Ireland during the period 1982-1996. DESIGN: Surveillance data on pre-AIDS and AIDS deaths reported to the PHLS-AIDS Centre were analysed. METHODS: Pre-AIDS mortality was estimated as the proportion of pre-AIDS deaths among all deaths in HIV-infected people. Trends over time in the number of pre-AIDS and AIDS deaths were compared using Poisson regression with logarithmic link. Causes of pre-AIDS deaths were recorded. Comparisons were made between the pre-AIDS and the AIDS death groups by logistic regression for: age, location of residence at death, year of death and risk exposure. RESULTS: Four-hundred and sixty-eight pre-AIDS deaths and 8574 AIDS deaths were identified. Pre-AIDS mortality accounted for 5.0% of HIV-related deaths. Trends over time in the number of pre-AIDS and AIDS deaths were not significantly different (P=0.11). Reported causes of pre-AIDS death included pneumonia (92), liver disease (62), septicaemia (51), malignancies (49), suicide (45), cardiopulmonary causes (46), haemorrhage (42), overdose (24) and accidental causes (24). Factors positively associated with pre-AIDS death were injecting drug use, haemophilia and blood transfusion, residence outside the Thames regions, and death at an older age. CONCLUSIONS: Pre-AIDS mortality represents a substantial proportion of HIV mortality, particularly where injecting drug use is a frequent route of HIV transmission.

CD4 cell counts in adults with newly diagnosed HIV infection: results of surveillance in England and Wales, 1990-1998. CD4 Surveillance Scheme Advisory Group.

OBJECTIVES: To describe the distribution and changes in CD4 cell counts (both initial and subsequent) in HIV-infected persons over time and determine the factors influencing these counts. DESIGN: Reports were requested from laboratories measuring CD4 cell counts in England and Wales. Initial counts were analysed and median counts were followed over time. METHODS: Time trends and the relationship between initial CD4 cell count and age, sex, and HIV risk category were studied using quantile regression methods or chi-square tests. RESULTS: Between 1990 and 1998, 9553 adults were newly diagnosed with HIV infection and had a CD4 cell count within 6 months of HIV diagnosis. Over 50% of initial CD4 cell counts in each major risk category were below 350 cells/mm3. Older age (P < 0.001), male sex (P < 0.013) and heterosexual risk (P < 0.001) were independently associated with lower initial CD4 cell counts. For heterosexually infected adults, the median initial CD4 cell count was significantly negatively associated with the year of diagnosis (P = 0.03) and the median age increased through the time period examined (P < 0.001), whereas for men who have sex with men (MSM), there was no significant change in these values over time. For each year cohort of newly diagnosed individuals, the median CD4 cell count in subsequent years decreased until 1996 and then increased thereafter, consistent with a treatment effect. CONCLUSION: Across all major risk groups, a large proportion of HIV-infected adults are being diagnosed late in the course of HIV disease. For the heterosexually infected, the data suggest an ageing cohort effect, whereas for MSM the data are consistent with continuing transmission.

Improved survival from diagnosis of AIDS in adult cases in the United Kingdom and bias due to reporting delays.

OBJECTIVE: To measure developments in survival patterns among United Kingdom adult AIDS cases. DESIGN: A follow-up survey of cases reported voluntarily to the national surveillance schemes was undertaken to obtain up-to-date information on vital status. METHODS: All reporting clinicians who had a current AIDS patient not known to have died whose AIDS-defining illness was diagnosed before the end of September 1990 were contacted. A total of 3984 cases were included in the analysis. RESULTS: An extra third of deaths other than those reported through routine channels were ascertained by follow-up. Median survival for patients diagnosed before and after the end of 1986 increased from 15 to 18 months for men who had sex with men presenting with Kaposi's sarcoma, from 10 to 19 months for other men who had sex with men and from 7 to 16 months for all others. Improvement in survival was greatest in the first 3 months. One-third of patients have been surviving 2 years or more. Factors observed with independent effects on improved survival are recent diagnosis, younger age and larger cumulative AIDS case load of reporting centre. HIV encephalopathy and other central nervous system symptoms may be associated with poorer survival. CONCLUSIONS: Survival patterns have been changing and generally improving. Average survival for very recent cohorts tends to be underestimated because longer survival has been observed in patients for whom there is a longer delay between AIDS diagnosis and report to the Communicable Disease Surveillance Centre. Information on mortality is improved by active follow-up.

Birth weight and special educational needs: effects of an increase in the survival of very low birthweight infants in London.

OBJECTIVES: To assess the contribution of children with different birth weights to special educational needs within a single health district, and to determine whether this pattern changed over the time when the survival of very low birthweight (VLBW) infants was increasing. SETTING: An inner London health district. STUDY DESIGN: A cohort of children born to local parents between January 1974 and December 1980 was selected from birth notifications, including only those infants who survived for more than one month. Community child health records were then inspected to identify children from the cohort who had been formally assessed for special educational needs before their 8th birthday. The risk of special educational needs was compared for the years 1974-77 and 1977-80 (the first and second halves of the period studied). SUBJECTS: The infant cohort consisted of 31,846 children. Altogether 260 (0.8%) of these were later assessed formally. RESULTS: VLBW infants were 4.4 times more likely to be assessed than normal birthweight infants. Formal assessment within the district occurred in three of 68 VLBW infants from the first half of the period studied, and three of 120 from the second half. CONCLUSION: Although VLBW infants are at higher risk, an increase in their survival was not associated with any increase in their contribution to the group with special educational needs within our district. Their contribution, as a group, to the total number of children with special educational needs is very small.

The normal glenohumeral relationships. An anatomical study of one hundred and forty shoulders.

We measured the dimensions of the humeral and glenoid articular surfaces in 140 shoulders that were representative of a given population of patients, and also evaluated several glenohumeral relationships. Ninety-six measurements were made in the shoulders of cadavera and forty-four, on magnetic resonance-imaging studies of living patients. Eighty-five per cent of the humeral measurements fell within eight fixed combinations of the radius of curvature and the thickness of the humeral head, in two-millimeter increments. The average radius of curvature of the humeral head in the coronal plane was 24 +/- 2.1 millimeters (range, nineteen to twenty-eight millimeters). The average thickness of the humeral head was 19 +/- 2.4 millimeters (range, fifteen to twenty-four millimeters). There was a wide variability in the size of the humeral head and a direct correlation between the differences in size and the heights in both men and women. The humeral articular surface was spherical in the center; however, the peripheral radius was two millimeters less in the axial plane than in the coronal plane. Thus, the peripheral contour of the articular surface was elliptical (ratio, 0.92). The radius of curvature of the glenoid, measured in the coronal plane, was an average of 2.3 +/- 0.2 millimeters greater than that of the humeral head. The average dimensions of the glenoid in the superior-inferior and anterior-posterior (lower half) directions were 39 +/- 3.5 millimeters (range, thirty to forty-eight millimeters) and 29 +/- 3.2 millimeters (range, twenty-one to thirty-five millimeters). The anterior-posterior dimension of the glenoid was pear-shaped, the lower half being larger than the top half. The ratio of the lower half to the top half was 1:0.80 +/- 0.01. There was a strong linear correlation between the lateral humeral offset and the size of the humeral head (radius of curvature and thickness). The average lateral humeral offset was 56 +/- 5.7 millimeters (range, forty-three to sixty-seven millimeters). The superior most point on the humeral articular surface was an average of 8 +/- 3.2 millimeters (range, three to twenty millimeters) cephalad to the top of the greater tuberosity. Our data show that reconstruction of the lateral humeral offset is important in optimization of the moment arm of the deltoid and rotator cuff and of the normal tension of the soft tissue after prosthetic reconstruction.

Increasing incidence of cryptococcosis in the United Kingdom.

The incidence of infection with Cryptococcus neoformans in the United Kingdom during the years between 1953 and 1981 is compared with that between 1982 and 1991. The patients were those from whom samples were submitted to the PHLS Mycological Reference Laboratory (MRL), or those in whom the disease was confirmed elsewhere in the United Kingdom and reported to PHLS Communicable Disease Surveillance Centre (CDSC). In all, 83 cases were identified between 1953 and 1981 and 322 between 1982 and 1991, 201 of which were known to be HIV-associated. The incidence of infection with Cryptococcus neoformans has increased four-fold in the last decade. It is an increasing cause of infection in immunosuppressed patients, most notably those with HIV infection. Currently, 4.0% patients with AIDS in the United Kingdom are known to have developed cryptococcosis.

AIDS defining diseases in the UK: the impact of PCP prophylaxis and twelve years of change.

We examined all reports of adult AIDS cases made to the 2 national surveillance centres in the UK for changes in AIDS defining conditions between January 1982 and September 1994. Differences and changes among persons diagnosed since January 1988 who had and had not been aware of their HIV infection prior to their AIDS diagnosis were of particular interest. Pneumocystis carinii pneumonia (PCP) is the AIDS defining disease most often reported at the initial AIDS diagnosis. Its proportion of all AIDS cases has increased significantly between January 1982 and December 1987 and decreased markedly thereafter. Since January 1988 a significant decrease in the proportion of cases diagnosed with cryptosporidial infection was also observed while increases were observed in the proportion of cases diagnosed with: HIV wasting (chi(1)(2) = 5.56) PML (chi(1)(2) = 19.47), mycobacterium avium complex (chi(1)(2) = 35.76) and pulmonary tuberculosis (chi(1)(2) = 144.0). For cases diagnosed between January 1988 and September 1994, PCP was more likely to be diagnosed in patients previously unaware of their HIV infection (P < 0.01) as was extrapulmonary TB (P < 0.01). In contrast, the following diseases were more likely to be diagnosed in patients already aware of their HIV infection prior to the diagnosis of AIDS: oesophageal candidiasis (P < 0.001), HIV wasting (P = 0.07), mycobacterium avium complex (P = 0.0001), cytomegalovirus disease (P < 0.001), HIV encephalopathy (P = 0.0009) and cryptosporidial infection (P = 0.02). Prophylaxis and anti-retroviral therapy appear to have had a significant impact on the temporal changes of the most frequently diagnosed AIDS diseases. While PCP prophylaxis has substantially reduced the likelihood of a PCP diagnosis at AIDS, the corresponding increase in other opportunistic infections suggests that there may be a need for improved prophylaxis for these conditions.

Cement-within-cement revision hip arthroplasty.

We reviewed 19 revision hip arthroplasties in which the new femoral component had been recemented into the old, intact cement mantle. The mean time from the first operation to revision was 64 months and the average follow-up was 59 months. There were 7 excellent, 11 good, and one fair result. No femoral component had been revised for loosening and all the stems appeared radiographically stable. Complications included intraoperative perforation of the femur on two occasions and one dislocation. The use of the cement-within-cement technique requires that the old cement surface be dry and roughened to increase the surface area and that the cement be injected in the liquid phase to prevent lamination. The indications for this technique include a broken stem with an intact distal cement mantle, the removal of a femoral component for revision of a loose cup to improve exposure and/or increase offset, recurrent dislocation secondary to component malposition, and debonding of the femoral component within an intact cement mantle.

Evaluation of the painful total hip arthroplasty.

Total hip arthroplasty is a common technique for the surgical management of degenerative hip disease. Because of the increasing number of patients and the variety of prostheses and fixation modalities available to the surgeon, the evaluation of the patient with a painful arthroplasty has become an increasingly complex endeavor. The growing number of patients who undergo multiple revision surgeries further complicates the evaluation of the painful arthroplasty. Other complicating factors include the lack of absolute sensitivity and specificity of the variety of diagnostic techniques and the difficulty of differentiating pain caused by septic verses aseptic loosening. This report reviews the recent literature concerning the evaluation of the painful total hip arthroplasty and provides a clinical rationale for the assessment of the painful total hip arthroplasty.

The rationale for cemented total hip arthroplasty.

Long-term follow-up of early Charnley cemented THAs demonstrates excellent survival (Table 1). New techniques in cementing have improved the quality of the femoral cement fixation and have shown consistently good performance at 10-year follow-up. Noncemented designs have not yet demonstrated similar long-term results. Recent reports reveal osteolysis in noncemented prostheses, which is observed earlier than in cemented designs. This implies a greater role for polyethylene debris in the etiology of osteolysis. Polyethylene debris is produced not only at the articulation but also at the nonarticular metal-polyethylene interface in modular metal-backed acetabular components. This results in the production of additional plastic debris. Metal backing has not demonstrated any clinical improvement in the long-term performance of cemented acetabular components. Furthermore, it may be detrimental due to decreased polyethylene thickness, increased stress within the polyethylene, and an increased rate of polyethylene wear of both the articular and nonarticular surfaces. Multiple reports have demonstrated that titanium alloy is not an acceptable articulating surface because it has a poor resistance to abrasion. It can result in severe metallosis in the periarticular tissues, leading to progressive osteolysis and early failure of the arthroplasty. Caution is suggested in the widespread application of polymodular femoral components because the production of metallic debris may prove excessive. Cemented THA remains the gold standard by which other methods of fixation must be assessed. The enviable long-term results with early cementing techniques and the Charnley prosthesis will be difficult to match, even with developing technology.

A summary of occupationally acquired HIV infections described in published reports to December 1997.

Since the first case of documented seroconversion after a specific occupational exposure to HIV was reported in 1984, national or regional systems for the surveillance of occupationally acquired HIV infection have been developed in many industrialised cou

Total hip replacement in the elderly: cost-effective alternatives.

The cost of the prosthetic components can represent approximately 15% to 25% of the total cost of hospitalization, depending upon whether cemented or cementless fixation is selected. The excellent long-term clinical data of cemented fixation and the cost of the implants clearly favor cemented fixation for total hip arthroplasty in the elderly patient.

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.

Factors associated with lack of awareness of HIV infection before diagnosis of AIDS.

OBJECTIVE: To identify characteristics of people likely to be unaware of their HIV infection before diagnosis of AIDS defining disease. DESIGN: Survey of continuing surveillance of voluntarily reported AIDS cases. SUBJECTS: 4127 adults with AIDS diagnosed during 1989-92 and reported to the Public Health Laboratory Service AIDS Centre. SETTING: England and Wales. MAIN OUTCOME MEASURE: Lack of prolonged awareness of infection before diagnosis of AIDS, defined as an interval of nine months or less between first positive test result and diagnosis of AIDS. RESULTS: Of 3556 adults with known dates of first positive HIV test result and AIDS diagnosis, 1742 (49%) had been unaware of their infection for up to nine months before AIDS was diagnosed. Lack of awareness was independently and positively associated with infection through heterosexual contact (odds ratio 4.46, 95% confidence interval 3.15 to 6.33), AIDS reported outside the Thames regions (1.64, 1.38 to 1.96), and being non-white (1.99, 1.51 to 2.61). Women were less likely to be unaware than men (0.50, 0.33 to 0.76), and people diagnosed in 1992 were least likely to be unaware (0.48, 0.39 to 0.60). Those aged 25-49 years at diagnosis were less likely to be unaware than those aged 15-24 years and those aged 50 and over. CONCLUSIONS: People with certain characteristics are more likely than others to be unaware of their HIV infection before AIDS is diagnosed and are therefore less likely to receive prophylaxis. Methods for educating this heterogeneous group need to be investigated.

HIV antibody assay that gave false negative results: multicentre collaborative study.

OBJECTIVE: To identify false negative results arising from the use of a commercial kit to detect antibody to HIV-1 and HIV-2 between July 1995 and March 1996. DESIGN: The 56 laboratories in the United Kingdom that were using the assay were asked to retrieve and retest specimens with an alternative assay for HIV-1 and HIV-2. Details of false negative results were obtained and these serum samples further investigated. SUBJECTS: 24,181 patients tested with the assay who were reported as being negative for HIV antibody. An additional 497 patients were confirmed as HIV positive with the assay. RESULTS: Serum samples of 20,973 of the patients were retested, and four patients were found to have had false negative results with the kit; three further patients were found to have had false negative results in the course of other laboratory testing. The seven patients with false negative results with the kit were of diverse risk group and HIV-1 subtype. Four had evidence of recent HIV infection. CONCLUSION: The commercial kit had a sensitivity of 99.2% (497/501), or less if the additional three patients with false negative results were taken into account.

Sexually transmitted diseases and HIV-1 infection among homosexual men in England and Wales.

OBJECTIVE: To examine surveillance data for evidence of changing sexual behaviour and continuing transmission of HIV-1 among men who have sex with men. DESIGN: Analytic study of surveillance data on sexually transmitted diseases. SETTING: England and Wales. MAIN OUTCOME MEASURES: Number of cases of rectal gonorrhoea and newly diagnosed HIV infection in homosexual men. RESULTS: New cases of gonorrhoea among men attending genitourinary medicine clinics increased by 7.7% in 1989 and by 4.2% in 1990. Reports of rectal isolates of Neisseria gonorrhoeae also rose and the male to female ratio for patients with rectal gonorrhoea changed from 0.3:1 during 1988-9 to 2.6:1 in 1990-1. Although the overall number of cases of acute hepatitis B fell during 1988-91, 81 and 82 homosexual men were infected in 1990 and 1991 respectively compared with 50 and 42 in 1988 and 1989. 1526 men had HIV-1 infection diagnosed in 1991, the largest number since 1987. Twenty eight of the 97 (29%) men who seroconverted between January 1989 and December 1991 were aged less than 25. The proportion of men aged 15-19 who were found to be infected with HIV-1 at their first test increased from an average of 2.4% up to 1990 to 4.7% in the first nine months of 1991. The prevalence of HIV infection in men under 25 attending genitourinary medicine clinics in London was 17% compared with 7.8% outside London. CONCLUSION: Unsafe sexual behaviour and HIV transmissions have increased among homosexual men after a period of decline. Recent HIV transmissions may disproportionately affect younger men.