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Overall HIV Prevalence

HIV Prevalence

The overall prevalence of HIV includes the number of diagnosed as well as undiagnosed people infected with HIV. In the UK, estimates of undiagnosed infections rely on data from unlinked anonymous (UA) surveys conducted in three selected adult populations: pregnant women, injecting drug users and  sexual health clinic attendees. These data, in addition to other surveillance and sexual behaviour data are fed into a Multi-Parameter Evidence Synthesis (MPES) model which provides national prevalence estimates.

MPES Model-Based Estimates of HIV Prevalence in the UK in 2009

National estimates of the number of individuals living with HIV in the UK are obtained from a complex statistical model fitted to an ensemble of surveillance and survey-type prevalence data. The model posits a subdivision of the target UK population aged 15-59 years into key mutually exclusive exposure subgroups, and produces estimates by geographical region, infection diagnosis status and gender: these are organised in Tables 1 and 2. Details of the model structure and its underlying assumptions can be found in Goubar et al. (2008) and Presanis et al. (2008), and a more extensive analysis of trends in HIV infections and prevalence can be found in Presanis et al. (2010) (Full references in PDF below). Data sources used to inform the model include the Unlinked Anonymous (UA) seroprevalence surveys, the Survey of Prevalent HIV Infections Diagnosed (SOPHID), HIV and AIDS New Diagnoses and Deaths surveillance, and the Gay Men's Sexual Health Survey.

The estimated ratio of diagnosed to undiagnosed HIV infection among 15 to 59 year olds is applied to the population that falls outside this age-range to obtain an overall number of people living with HIV in the United Kingdom. This estimated number is presented in our latest HIV annual report.

Unlinked Anonymous Surveys

The unlinked anonymous monitoring surveys provide data on the prevalence of HIV in selected adult populations (pregnant women, injecting drug users and genitourinary medicine clinic attendees). These surveys include those people who have already been diagnosed with HIV infection as well as people who are currently undiagnosed and would therefore not be included in other surveillance systems. The primary objective of the unlinked anonymous monitoring surveys is to monitor trends in the prevalence of both diagnosed and undiagnosed HIV infection. Since the surveys began in 1990, approaching ten million samples have been irreversibly unlinked and anonymised from patient identifying information and tested for HIV infection.


Annual Report and Related Information


 


 

Related Information