Longitudinal study of infectious intestinal disease in the UK (IID2 study): incidence in the community and presenting to general practice.

OBJECTIVES: To estimate, overall and by organism, the incidence of infectious intestinal disease (IID) in the community, presenting to general practice (GP) and reported to national surveillance. DESIGN: Prospective, community cohort study and prospective study of GP presentation conducted between April 2008 and August 2009. SETTING: Eighty-eight GPs across the UK recruited from the Medical Research Council General Practice Research Framework and the Primary Care Research Networks. PARTICIPANTS: 6836 participants registered with the 88 participating practices in the community study; 991 patients with UK-acquired IID presenting to one of 37 practices taking part in the GP presentation study. MAIN OUTCOME MEASURES: IID rates in the community, presenting to GP and reported to national surveillance, overall and by organism; annual IID cases and GP consultations by organism. RESULTS: The overall rate of IID in the community was 274 cases per 1000 person-years (95% CI 254 to 296); the rate of GP consultations was 17.7 per 1000 person-years (95% CI 14.4 to 21.8). There were 147 community cases and 10 GP consultations for every case reported to national surveillance. Norovirus was the most common organism, with incidence rates of 47 community cases per 1000 person-years and 2.1 GP consultations per 1000 person-years. Campylobacter was the most common bacterial pathogen, with a rate of 9.3 cases per 1000 person-years in the community, and 1.3 GP consultations per 1000 person-years. We estimate that there are up to 17 million sporadic, community cases of IID and 1 million GP consultations annually in the UK. Of these, norovirus accounts for 3 million cases and 130,000 GP consultations, and Campylobacter is responsible for 500,000 cases and 80,000 GP consultations. CONCLUSIONS: IID poses a substantial community and healthcare burden in the UK. Control efforts must focus particularly on reducing the burden due to Campylobacter and enteric viruses.

A synthesis of convenience survey and other data to estimate undiagnosed HIV infection among men who have sex with men in England and Wales.

BACKGROUND: Hard-to-reach population subgroups are typically investigated using convenience sampling, which may give biased estimates. Combining information from such surveys, a probability survey and clinic surveillance, can potentially minimize the bias. We developed a methodology to estimate the prevalence of undiagnosed HIV infection among men who have sex with men (MSM) in England and Wales aged 16-44 years in 2003, making fuller use of the available data than earlier work. METHODS: We performed a synthesis of three data sources: genitourinary medicine clinic surveillance (11 380 tests), a venue-based convenience survey including anonymous HIV testing (3702 MSM) and a general population sexual behaviour survey (134 MSM). A logistic regression model to predict undiagnosed infection was fitted to the convenience survey data and then applied to the MSMs in the population survey to estimate the prevalence of undiagnosed infection in the general MSM population. This estimate was corrected for selection biases in the convenience survey using clinic surveillance data. A sensitivity analysis addressed uncertainty in our assumptions. RESULTS: The estimated prevalence of undiagnosed HIV in MSM was 2.4% [95% confidence interval (95% CI 1.7-3.0%)], and between 1.6% (95% CI 1.1-2.0%) and 3.3% (95% CI 2.4-4.1%) depending on assumptions; corresponding to 5500 (3390-7180), 3610 (2180-4740) and 7570 (4790-9840) men, and undiagnosed fractions of 33, 24 and 40%, respectively. CONCLUSIONS: Our estimates are consistent with earlier work that did not make full use of data sources. Reconciling data from multiple sources, including probability-, clinic- and venue-based convenience samples can reduce bias in estimates. This methodology could be applied in other settings to take full advantage of multiple imperfect data sources.

Sexual risk behaviour and knowledge of HIV status among community samples of gay men in the UK.

OBJECTIVES: Undiagnosed infection presents a potential risk for the onward transmission of HIV and denies men early interventions for their health. Little is known about the differences between men who are, and are not, aware of their HIV status in the UK. METHODS: Cross-sectional surveys of men in commercial gay venues in London, Brighton, Manchester, Glasgow, and Edinburgh (2003-2005). Anonymous, self-completion questionnaires, and oral fluid samples (tested for HIV antibodies) were obtained from 3672 men (61% response rate). RESULTS: Of 3501 men with a confirmed positive or negative oral fluid result, 318 were HIV positive (9.1%). Of these, 131 (41.2%) were undiagnosed; 81.1% of men with undiagnosed HIV had previously tested (92.2% tested negative; the remainder did not know the result); 62.3% still thought that they were negative. Undiagnosed and diagnosed men reported greater sexual risk and sexually transmitted infections than HIV-negative men. Compared with HIV-negative men, the adjusted odds ratio of unprotected anal intercourse with two or more partners was higher among undiagnosed men (odds ratio 2.21, 95% confidence interval 1.17-4.20), but highest among diagnosed men (odds ratio 6.80, 95% confidence interval 4.39-10.52). CONCLUSION: A high proportion of the HIV-positive men were undiagnosed and not receiving benefits of clinical care, but sexual risk and sexually transmitted infections were highest among men who were aware of their HIV-positive status. Clinics should proactively offer testing to reduce undiagnosed HIV, target repeat testing at high-risk men who have previously tested negative, and initiate evidence-based behavioural interventions to reduce sexual risk among men living with diagnosed HIV as well as those testing negative.

A tale of three cities: persisting high HIV prevalence, risk behaviour and undiagnosed infection in community samples of men who have sex with men.

OBJECTIVES: To examine the geographical variations in HIV prevalence (diagnosed and undiagnosed), use of sexual health services, sexually transmitted infections and sexual behaviour in a community sample of men who have sex with men in three cities in England, specifically London, Brighton and Manchester. METHODS: Cross-sectional surveys of men visiting gay community venues in three large cities in England. Men self-completed a questionnaire and provided an anonymous oral fluid sample for HIV antibody testing. RESULTS: HIV prevalence ranged from 8.6% to 13.7% in the three cities. Over one-third of HIV infection remained undiagnosed in all sites despite 69% of HIV-positive men reporting attending a genitourinary medicine clinic in the last year. Similar and high levels of risk behaviour were reported in all three cities. 18% of HIV-negative men and 37% of HIV-positive men reported unprotected anal intercourse with more than one partner in the last year. 20% of negative men and 41% of positive men reported an STI in the last year. CONCLUSIONS: Across all cities, despite widespread availability of anti-retroviral treatment and national policy to promote HIV testing, many HIV infections remain undiagnosed. Data from this community sample demonstrate high levels of risk behaviour and STI incidence, especially among those who are HIV positive. Renewed efforts are needed to increase diagnosis and to reduce risk behaviour to stem the continuing transmission of HIV.

Increases in HIV-related sexual risk behavior among community samples of gay men in London and Glasgow: how do they compare?

OBJECTIVE: In this paper, we compare trends in sexual risk among gay men in the largest city in England (London) and the largest city in Scotland (Glasgow). METHODS: Self-complete questionnaires administered to representative samples of men visiting the commercial gay scenes in London and Glasgow in 1996, 1999, and 2002 (N = 8247). RESULTS: Multivariate logistic regression was used to assess the trends in unprotected anal intercourse (UAI), UAI with partners of unknown/discordant HIV status, and UAI with more than 1 partner. Each increased significantly in 1999 and 2002 in London, but only in 2002 in Glasgow. Testing for HIV also increased significantly in London, but not in Glasgow. Overall, HIV testing levels were considerably lower in Glasgow (in 2002, 49.1% vs. 74.6% in London). Overall, sexual risk was higher in London, but UAI with partners of unknown/discordant HIV status was higher in Glasgow (in 2002, 27.4% vs. 21.3%). CONCLUSIONS: Although the same pattern of increase in HIV-related sexual risk behavior was apparent in the cities, differences in HIV testing and nonconcordant UAI suggest different HIV prevention needs and that targeted health promotion interventions are required in London and Glasgow. City-specific factors should be considered in the development of appropriate sexual health interventions.