Comparative analysis of the serum microbiome of HIV infected individuals

HIV infects the CD4 cells which marks the suppression of our immune system. DNA from serum of healthy, treated and untreated HIV infected individuals was extracted. The DNA was subjected to 16S metagenomic sequencing and analyzed using QIIME2 pipeline. 16S sequencing analysis showed serum microbiome was dominated by Firmicutes, Proteobacteria, Bacteroidota and Actinobacteria. Treated HIV infection showed highest abundance of Firmicutes (66.40%) significantly higher than untreated HIV infection (35.88%) and control (41.89%). Bacilli was most abundant class in treated (63.59%) and second most abundant in untreated (34.53%) while control group showed highest abundance of class Gamma-proteobacteria (45.86%). Untreated HIV infection group showed Enterococcus (10.72%) and Streptococcus (6.599%) as the most abundant species. Untreated HIV infection showed significantly higher (p = 0.0039) species richness than treated and control groups. An altered serum microbiome of treated HIV infection and higher microbial abundance in serum of untreated HIV infection was observed.     

Clinical Manifestations and the Natural History of HIV Infection in Adults

The clinical expression of infection with the human immunodeficiency virus (HIV) appears increasingly complex. It includes manifestations due to opportunistic diseases, as well as illness directly caused by HIV itself. Neurologic disease may include involvement of the brain, spinal cord and peripheral nerves and is probably directly caused by HIV, as is lymphocytic interstitial pneumonia. The etiology of the chronic diarrhea and a papular pruritic skin eruption associated with HIV infection is unclear. Between 2% and 8% of HIV-infected persons progress to the acquired immunodeficiency syndrome (AIDS) per year, with no apparent decrease in the rate of disease progression over time. A chronically activated state secondary to chronic microbial antigenic exposure may increase both the susceptibility to HIV infection and development of disease. Increased HIV gene expression, followed by persistent antigenemia, appear to be triggering factors in clinical deterioration. The role, if any, of environmental and/or genetic cofactors remains unclear.     

The usefulness of defined clinical features in the diagnosis of HIV/AIDS infection in Sierra Leone.

Sierra Leone ranks at the bottom of the global World Bank Development Index based on multiple health and economic indices and lacks the resources to purchase HIV diagnostic kits. Our study has defined some common clinical features presenting HIV infection that could form clinical algorithms for the diagnosis and recognition of HIV infection by health workers in Sierra Leone. In a private clinic in Freetown, Sierra Leone, West Africa, 106 out of a total of 124 patients presenting with various symptoms and strong clinical suspicion of HIV infection within a two-year period (1999 and 2000), were deemed positive by two different ELISA tests. The prevalence of HIV infection seen in this private clinic in Freetown in 2000 was 14.89% as compared to 9.25% in 1999. The positive predictive value of our clinical diagnosis of HIV/AIDS infection was 85.5%. The male:female ratio of the patients in our series was 1:1.9, with a mean age of 39 years for males and 28 years for females. HIV infection was found in a cross-section of the population that we examined. Heterosexual contact appeared to be the major mode of transmission amongst our patients and there seemed to be a significant epidemiological risk of HIV infection amongst those who traveled to other countries in the West African sub region. Common clinical features in decreasing frequency were fever (92.5%), weight loss (84.1%), lymphadenopathy (78.3%), cough (48.1%), diarrhea (37.7%), candidiasis (32.1%) and body aches (30.1%).     

Evaluation of the Bio-Rad Geenius HIV 1/2 Confirmation Assay as an Alternative to Western Blot in the Korean Population: A Multi-Center Study

Recently updated recommendations for diagnosis of HIV infection suggest a new diagnostic algorithm including HIV-1/HIV-2 antibody differentiation immunoassay instead of western blot (WB) as a confirmatory testing. We evaluated Bio-Rad Geenius HIV1/2 confirmation assay as a simple and reliable alternative to WB in the Korean population with low HIV prevalence. The Geenius HIV1/2 was performed in a total of 192 serum specimens (140 reactive and 52 nonreactive specimens by ARCHITECT HIV Ag/Ab Combo assay) that were prospectively collected from five institutions. HIV-1 nucleic acid amplification test (NAT) was performed in negative or indeterminate specimens by Geenius HIV1/2 or WB. Among 140 reactive specimens by HIV Ag/Ab assay, 82 (58.6%) were positive for HIV-1 Ab by Geenius HIV1/2. Among 58 negative or indeterminate specimens by Geenius HIV1/2, four specimens (6.9%) were positive by HIV-1 NAT. The sensitivity and specificity of Geenius HIV1/2 were 95.3% and 100.0%, respectively. When we considered only WB, the sensitivity and specificity of Geenius HIV1/2 were 100.0% and 99.1%, respectively. Agreement between Geenius HIV1/2 and WB was excellent (weighted Kappa = 0.89). The Geenius HIV1/2 is simple and time-saving compared with WB. It has an excellent performance and can be a reliable alternative to WB. HIV-1 NAT should be performed in negative or indeterminate specimens by Geenius HIV1/2 to detect acute HIV infection as recommended in new HIV testing algorithms.     

Multi-Centre Evaluation of the Determine HIV Combo Assay when Used for Point of Care Testing in a High Risk Clinic-Based Population

Background

Determine HIV Combo (DHC) is the first point of care assay designed to increase sensitivity in early infection by detecting both HIV antibody and antigen. We conducted a large multi-centre evaluation of DHC performance in Sydney sexual health clinics.

Methods

We compared DHC performance (overall, by test component and in early infection) with conventional laboratory HIV serology (fourth generation screening immunoassay, supplementary HIV antibody, p24 antigen and Western blot tests) when testing gay and bisexual men attending four clinic sites. Early infection was defined as either acute or recent HIV infection acquired within the last six months.

Results

Of 3,190 evaluation specimens, 39 were confirmed as HIV-positive (12 with early infection) and 3,133 were HIV-negative by reference testing. DHC sensitivity was 87.2% overall and 94.4% and 0% for the antibody and antigen components, respectively. Sensitivity in early infection was 66.7% (all DHC antibody reactive) and the DHC antigen component detected none of nine HIV p24 antigen positive specimens. Median HIV RNA was higher in false negative than true positive cases (238,025 vs. 37,591 copies/ml; p = 0.022). Specificity overall was 99.4% with the antigen component contributing to 33% of false positives.

Conclusions

The DHC antibody component detected two thirds of those with early infection, while the DHC antigen component did not enhance performance during point of care HIV testing in a high risk clinic-based population.     

Prevention and control of HIV infection in the Osh region of the Kyrgyz Republic

A total of 178 cases of HIV infection were diagnosed in the Osh region of the Kyrgyz Republic for January 1, 2003, the intensity of the prevalence of HIV infection being 14.5 per 100,000 of the population with this figure for the whole republic being equal to 5.9. In the dynamics of the HIV infection epidemic two periods were detected. During the first 3 years (1998-2000) a few individual imported cases of HIV infection were registered in the region. During the last 2 years (2001-2002) 98.8% of all cases of HIV infection registered in the region, as well as the presence of an epidemic outbreak among injection drug users (IDU), were detected. The risk factors of getting HIV infection were the intravenous use of drugs and a low level of information among young people concerning the routes of transmission of this infection and means of protection from HIV/AIDS: the promotion of healthy life style among young people, the introduction of the programs of "harm reduction" among IDU and the rules of safe sex.     

The characteristics of the course of tuberculosis in HIV-infected patients and prophylactic measures

Morbidity in HIV infection and tuberculosis in persons having these two infections in association was analyzed. According to the data for the end of the first quarter of 1997 the presence of association of HIV infection with tuberculosis was found in 91 patients. In 70.3% of cases HIV infection was contacted before the appearance of tuberculosis and in 18.7% of cases, after it; in 11% of cases the order of appearance of these two diseases could not be established. The study revealed that the markedness of the clinical picture of tuberculosis was determined by the progress of HIV infection.     

HIV infection in Saint Petersburg: the changing face of the epidemic

The specific features of the epidemiological situation in St. Petersburg at the first stage (1987-1995) and the second stage (1986-1999) of the development of HIV infection are described. During this period morbidity in HIV infection, starting from the insignificant rate of growth, sharply increased. For the first time injecting drug users were noted to come out to the foreground in the structure of the contingent of persons affected by HIV infection (57.5% and 72.6% in 1998 and 1999 respectively). Such change on the epidemic situation requires corrections in the strategy and tactics of preventive measures and medical assistance. To control HIV infection among drug users, only the combination of medical assistance given by narcologists with the realization of all elements of the program "Harm Reduction" can be effective.     

Opsonization of HIV with complement enhances infection of dendritic cells and viral transfer to CD4 T cells in a CR3 and DC-SIGN-dependent manner

In the present study, we demonstrated that opsonization of primary HIV-1 with human complement enhances infection of immature monocyte-derived dendritic cells (iDC) and transmission in trans of HIV to autologous CD4(+) T lymphocytes. Infection of iDC by opsonized primary R5- and X4-tropic HIV was increased 3- to 5-fold as compared with infection by the corresponding unopsonized HIV. Enhancement of infection was dependent on CR3 as demonstrated by inhibition induced by blocking Abs. The interaction of HIV with CCR5 and CXCR4 on iDC was affected by opsonization. Indeed, stromal-derived factor-1 was more efficient in inhibiting infection of iDC with opsonized R5-tropic HIV-1(BaL) (45%) than with heat-inactivated complement opsonized virus and similarly RANTES inhibited more efficiently infection of iDC with opsonized X4-tropic HIV-1(NDK) (42%) than with heat-inactivated complement opsonized virus. We also showed that attachment of complement-opsonized virus to DC-specific ICAM-grabbing nonintegrin (DC-SIGN) molecule on iDC and HeLa DC-SIGN(+) CR3(-) cells was 46% and 50% higher compared with heat-inactivated complement opsonized virus, respectively. Hence, Abs to DC-SIGN suppressed up to 80% and 60% the binding of opsonized virus to HeLa cells and iDC, respectively. Furthermore, Abs to DC-SIGN inhibited up to 70% of the infection of iDC and up to 65% of infection in trans of autologous lymphocytes with opsonized virus. These results further demonstrated the role of DC-SIGN in complement opsonized virus uptake and infection. Thus, the virus uses complement to its advantage to facilitate early steps leading to infection following mucosal transmission of HIV.     

Programmatic Cost Evaluation of Nontargeted Opt-Out Rapid HIV Screening in the Emergency Department

Background

The Centers for Disease Control and Prevention recommends nontargeted opt-out HIV screening in healthcare settings. Cost effectiveness is critical when considering potential screening methods. Our goal was to compare programmatic costs of nontargeted opt-out rapid HIV screening with physician-directed diagnostic rapid HIV testing in an urban emergency department (ED) as part of the Denver ED HIV Opt-Out Trial.

Methods

This was a prospective cohort study nested in a larger quasi-experiment. Over 16 months, nontargeted rapid HIV screening (intervention) and diagnostic rapid HIV testing (control) were alternated in 4-month time blocks. During the intervention phase, patients were offered HIV testing using an opt-out approach during registration; during the control phase, physicians used a diagnostic approach to offer HIV testing to patients. Each method was fully integrated into ED operations. Direct program costs were determined using the perspective of the ED. Time-motion methodology was used to estimate personnel activity costs. Costs per patient newly-diagnosed with HIV infection by intervention phase, and incremental cost effectiveness ratios were calculated.

Results

During the intervention phase, 28,043 eligible patients were included, 6,933 (25%) completed testing, and 15 (0.2%, 95% CI: 0.1%–0.4%) were newly-diagnosed with HIV infection. During the control phase, 29,925 eligible patients were included, 243 (0.8%) completed testing, and 4 (1.7%, 95% CI: 0.4%–4.2%) were newly-diagnosed with HIV infection. Total annualized costs for nontargeted screening were $148,997, whereas total annualized costs for diagnostic HIV testing were $31,355. The average costs per HIV diagnosis were $9,932 and $7,839, respectively. Nontargeted HIV screening identified 11 more HIV infections at an incremental cost of $10,693 per additional infection.

Conclusions

Compared to diagnostic testing, nontargeted HIV screening was more costly but identified more HIV infections. More effective and less costly testing strategies may be required to improve the identification of patients with undiagnosed HIV infection in the ED.     

An evaluation of the extent to which young people are informed about the acquired immunodeficiency syndrome

The data on the evaluation of the volume of information on the transmission routes of HIV infection, risk groups and prophylactic measures, acquired by young people aged 14-18 years, their attitude to different sources of information on AIDS, as well as the evaluation of the influence of lectures on the formation of their opinion of these problems, are presented. As found by questioning, 84.4-98.7% of adolescents who answered the questionnaires correctly indicated the routes of the transmission of HIV infection, prophylactic measures were known to 73.1-90.3%, risk groups were correctly defined by 80.6-98.0%, more than 70% of adolescents covered by questioning believed that mass media provided insufficient information on AIDS. In a group of adolescents given a lecture an increase in the number of correct answers and a decrease in the number of wrong answers on the transmission routes of HIV infection and on risk groups were registered.     

The determinants of the spread of HIV among injection drug addicts in Ukraine

The main tendencies in the development of drug addiction in the Ukraine, the dynamics of the spread of HIV among drug addicts introducing drugs intravenously, epidemiological data on HIV, AIDS and drug addiction, as well as prognoses on the development of HIV infection are presented. Since 1995 the number of HIV-infected persons grew 34-fold, the number of cases of HIV infection resulting from the intravenous use drugs rose to 70% simultaneously with the rise (about 34-fold) of the number of persons infected with HIV through sexual contacts (about 13 fold). In 1996-1997 such tendency increased. On the whole, the proportion of drug addicts introducing drugs by intravenous injection was 83% in the Ukraine. By April 1, 1998, official registration covered 18,800 HIV-infected persons, including 270 foreign nationals, as well as 499 AIDS patients, including 487 Ukrainian citizens, among them 28 children. Out of 18,800 HIV-infected persons, 78.3% were drug addicts, most of them young people aged 15-30 years; about 18% were young people under 20 years of age, 80% being males. According to the model the rapid spread of HIV from the group of drug addicts to the heterosexual population, the total number of HIV-infected persons reaching 1,500,000 is expected in the country by 2014.     

Impact of HIV infection on mortality in young men in a London health authority.

OBJECTIVE--To determine the number of deaths attributable to HIV infection among men aged 15-64 in a geographically defined population in the United Kingdom. DESIGN--Retrospective review of death certificates and linkage with local and national HIV and AIDS surveillance data. SETTING--Riverside District Health Authority, London. MAIN OUTCOME MEASURES--Numbers of deaths attributed to HIV infection in male residents of Riverside aged 15-64 and 15-44 over a six month period. Proportion of attributed deaths were (i) identified from death certificates by the Office of Population Censuses and Surveys as being due to HIV infection and (ii) reported as cases of AIDS or HIV related deaths to the Public Health Laboratory Service Communicable Disease Surveillance Centre. RESULTS--34 of 213 (16%) deaths in men aged 15-64 and 27 of 69 (39%) deaths in men aged 15-44 were attributed to HIV infection. Six of 33 (18%) attributed deaths were identified by the Office of Population Censuses and Surveys and 32/34 (94%) were reported to the Communicable Disease Surveillance Centre. CONCLUSIONS--HIV infection was the leading cause of death in male residents of Riverside aged 15-44 and the third commonest cause of death in those aged 15-64. Most individuals dying of known HIV infection were reported to the Communicable Disease Surveillance Centre but identification of the true cause of death from the process of death certification was poor. Measures to improve the certification of HIV and AIDS or the use of AIDS surveillance information correctly to code the cause of death needs to be considered to ensure that the true impact of HIV infection is reflected in routine mortality statistics.     

The results of sentinel epidemiological surveillance on the level of HIV prevalence among injection narcotic abusers in the city of Poltava

The sentinel epidemiological surveillance on the level of spread of HIV infection among injecting drug users in Poltava, taking part in the program of harm reduction, was carried out. The results of the surveillance revealed that the level of HIV infection among drug users was 37.8%, the level of HIV infection among females being higher than that among males. These data indicate that the level of HIV infection rises with the increase of age and the time of drug consumption. Still in the age group of 30 years and older and among drug addicts using drugs for 7 years and longer the lowest level of HIV infection was noted.     

A stochastic model for the development of an AIDS epidemic in a heterosexual population.

A non-age-dependent model, describing the evolution of a bisexual population, is developed in this paper and applied to projecting an AIDS epidemic in a heterosexual population. Included in the formulation are frequency- and non-frequency-dependent rules of partnership formation as well as five states of HIV disease, affecting the probability of infection per sexual contact. Results from computer experiments, designed to study the development of an AIDS epidemic in a heterosexual population fed by single males with a 50% prevalence of HIV infection prior to becoming active in heterosexual partnerships, are reported. In these experiments, the only source of HIV infection for females was sexual contacts with infected males within partnerships. Data on the probability of infection per sexual contact with an infected partner and the number of sexual contacts per month were incorporated into the model. However, the numbers used for the initial population of singles, couples, and those becoming sexually active per month were hypothetical. Even though the prevalence of HIV infection among males entering heterosexual partnerships was high, after 30 years the projected prevalence of HIV infection among females ranged from about 10 to 15% depending in part on the expected duration of partnerships and on whether the frequency- or non-frequency-dependent model was used. In these experiments, solutions of the embedded, nonlinear, deterministic equations for the incidence of HIV infection and the cumulative number of deaths due to AIDS proved to be good measures of central tendency for the sample functions of the stochastic population process.     

Genital human papillomavirus infection and associated penile intraepithelial neoplasia in males infected with the human immunodeficiency virus

OBJECTIVE: To investigate the association between human papillomavirus (HPV) infections and penile intraepithelial neoplasia (PIN) in genital lesions from human immunodeficiency virus (HIV)+ men. For comparison, we also investigated the same association using specimens from HIV- men. STUDY DESIGN: Imprint smears from penile lesions were obtained from 70 men (mean age, 30 years) who visited a dermatologist. Thirty of them were known to be HIV seropositive. Two study groups were formed: one of 40 HIV- and another of 30 HIV+ males. The smears were examined cytologically for HPV identification or PIN, immunocytochemically for HPV detection and by in situ hybridization for HPV typing. RESULTS: The rates of detecting HPV infection cytologically were higher among men with HIV infection (50%) than among their HIV-seronegative counterparts (30%). There was immunocytochemical evidence of HPV in HIV-infected men in a greater proportion (50%) than in HIV noninfected men (37.5%). By in situ hybridization it was found that there was a higher prevalence of potentially oncogenic HPV (16/18, 31/33/35): 75% in moderate or severe dysplasia (PIN 2 and 3) and 66.6% in HIV+ men as compared with HIV- men (10-16.6%). CONCLUSION: HIV-seropositive males showed an unbalanced distribution of HPV, with a predominance of "high-risk" HPV types. This suggests that immunodepression encourages infection by this oncogenic virus, thereby contributing to the frequency of precancerous lesions in HIV+ men.     

Estimating the Number of Persons Who Inject Drugs in the United States by Meta-Analysis to Calculate National Rates of HIV and Hepatitis C Virus Infections

Background

Injection drug use provides an efficient mechanism for transmitting bloodborne viruses, including human immunodeficiency virus (HIV) and hepatitis C virus (HCV). Effective targeting of resources for prevention of HIV and HCV infection among persons who inject drugs (PWID) is based on knowledge of the population size and disparity in disease burden among PWID. This study estimated the number of PWID in the United States to calculate rates of HIV and HCV infection.

Methods

We conducted meta-analysis using data from 4 national probability surveys that measured lifetime (3 surveys) or past-year (3 surveys) injection drug use to estimate the proportion of the United States population that has injected drugs. We then applied these proportions to census data to produce population size estimates. To estimate the disease burden among PWID by calculating rates of disease we used lifetime population size estimates of PWID as denominators and estimates of HIV and HCV infection from national HIV surveillance and survey data, respectively, as numerators. We calculated rates of HIV among PWID by gender-, age-, and race/ethnicity.

Results

Lifetime PWID comprised 2.6% (95% confidence interval: 1.8%–3.3%) of the U.S. population aged 13 years or older, representing approximately 6,612,488 PWID (range: 4,583,188–8,641,788) in 2011. The population estimate of past-year PWID was 0.30% (95% confidence interval: 0.19 %–0.41%) or 774,434 PWID (range: 494,605–1,054,263). Among lifetime PWID, the 2011 HIV diagnosis rate was 55 per 100,000 PWID; the rate of persons living with a diagnosis of HIV infection in 2010 was 2,147 per 100,000 PWID; and the 2011 HCV infection rate was 43,126 per 100,000 PWID.

Conclusion

Estimates of the number of PWID and disease rates among PWID are important for program planning and addressing health inequities.     

Factors Associated with HIV Prevalence and HIV Testing in Sierra Leone: Findings from the 2008 Demographic Health Survey

BackgroundThe Sierra Leone Demographic Health Survey 2008 found an HIV prevalence of 1.5%. This study investigates associations with HIV infection and HIV testing.MethodsHouseholds were selected using stratified multi-stage sampling. In all selected households women aged 15–49 were eligible. In every second household men aged 15–59 were also eligible. Participants were asked to consent for anonymous HIV testing. All participants interviewed and tested were analysed. Multiple logistic regression identified associations with HIV infection, undiagnosed infection and with ever having a voluntary HIV test among sexually active participants.ResultsOf 7495 invited 86% (6,475) agreed to an interview and HIV test. Among 96 HIV positive participants, 78% had never taken a voluntary HIV test so were unaware of their serostatus, and 86% were sexually active in the last 12 months among whom 96% did not use a condom at last intercourse. 11% of all participants had previously voluntarily tested. Among women who had tested, 60% did so in antenatal care. We found that those living in an urban area, and those previously married, were more likely to be HIV infected. Voluntary HIV testing was more common in those aged 25–44, living in an urban area, females, having secondary or higher education, having first sexual intercourse at age 17 years or older, and using condoms at last sex. Although 82% of men and 69% of women had heard of HIV, only 35% and 29% respectively had heard of antiretroviral therapy.ConclusionsThe HIV prevalence in Sierra Leone has been stable. HIV testing, however, is uncommon and most infected individuals are unaware of their serostatus. This could allow the epidemic to escalate as individuals with undiagnosed infection are unlikely to change their behaviour or access treatment. Improving knowledge and increasing testing need to remain central to HIV prevention interventions in Sierra Leone.     

Mycobacterium tuberculosis Complex and HIV Co-Infection among Extrapulmonary Tuberculosis Suspected Cases at the University of Gondar Hospital,Northwestern Ethiopia

Background

Extrapulmonary Tuberculosis (EPTB) and Human Immunodeficiency Virus (HIV) infection are interrelated as a result of immune depression. The aim of this study was to determine the prevalence of Mycobacterium tuberculosis complex isolates and the burden of HIV co-infection among EPTB suspected patients.

Method

An institution based cross-sectional study was conducted among EPTB suspected patients at the University of Gondar Hospital. Socio-demographic characteristics and other clinical data were collected using a pretested questionnaire. GeneXpert MTB/RIF assay was performed to diagnosis Mycobacterium tuberculosis complex and Rifampicin resistance. All samples were also investigated by cytology and culture. The HIV statuses of all patients were screened initially by KHB, and all positive cases were further re-tested by STAT-pack. Data was analyzed using SPSS version 20 computer software and a P-value of < 0.05 was taken as statistically significant.

Results

A total of 141 extrapulmonary suspected patients were enrolled in this study. The overall prevalence of culture confirmed extrapulmonary tuberculosis infection was 29.8%, but the GeneXpert result showed a 26.2% prevalence of Mycobacterium tuberculosis complex infection. The 78.4% prevalence of extrapulmonary tuberculosis infection was found to be higher among the adult population. The prevalence of HIV infection among EPTB suspected patients was 14.1%, while it was 32.4% among GeneXpert-confirmed extrapulmonary TB cases (12/37). Tuberculosis lymphadenitis was the predominant (78.4%) type of EPTB infection followed by tuberculosis cold abscess (10.7%). Adult hood, previous history of contact with known pulmonary tuberculosis patients, and HIV co-infection showed a statistically significant association with extrapulmonary tuberculosis infection (P<0.013).

Conclusion

The prevalence of culture confirmed-EPTB infection was high, and a higher EPTB-HIV co-infection was also observed.     

Trends in sexual behaviour and risk factors for HIV infection among homosexual men, 1984-7.

To assess whether the spread of infection with HIV can be reduced by changes in behaviour among groups most at risk because of their sexual practices sexual behaviour was monitored among 1050 homosexual men tested for HIV infection at a genitourinary medicine clinic in west London from November 1984 to September 1987. Four cohorts, defined by date of presentation, were studied by questionnaire at their presentation, and blood samples were analysed. Between the first and last cohorts there was a considerable fall in the proportion reporting casual relationships (291/329 (88%) v 107/213 (50%] and high risk activities, such as anoreceptive intercourse with casual partners (262/291 (90%) v 74/106 (70%], with the greatest changes occurring before the government information campaign began in 1986. Nevertheless, half of the men in the last cohort studied reported having casual partners. Multiple logistic regression showed that behavioural risk factors for HIV infection most closely resembled those for hepatitis B and that previous sexually transmitted diseases (syphilis, hepatitis B, and anogenital herpes) were themselves independent risk factors. A history of syphilis ranked above anoreceptive intercourse as the strongest predictor of HIV infection. Actively bisexual men showed a much lower prevalence of HIV infection (3/57, 5%) than exclusively homosexual men (113/375, 30%). Sexual behaviour among homosexual men changed during the period studied, and the incidence of HIV infection fell, although more education programmes directed at homosexual men are needed to re-emphasise the dangers of infection.