Reduce Numbers Undiagnosed
posted: 15/11/2010
The number of people in England and Wales who do not know they have HIV stayed the same between 2001 and 2008, despite more people being diagnosed with HIV.
Many of the people with HIV in the UK do not know this yet and undiagnosed people are much more likely to pass on HIV than people who are tested, advised about safer sex and treated.
To prevent onward HIV transmission we need to minimise the number of people with HIV who are undiagnosed and for how long people are undiagnosed.
A new study by the Medical Research Council, published in AIDS, estimates the total number of HIV positive people living in England and Wales aged 15-44, both diagnosed and undiagnosed, has increased from 32,400 in 2001 to 54,500 in 2008. Much of this rise is because more people are taking HIV tests.
Rise in diagnosed
The proportion of HIV infections diagnosed rose from 58 per cent in 2001 to 71 per cent in 2008, but the estimated number of people with HIV who have not been diagnosed has not fallen, because HIV infections are continuing to happen. Dr Anne Presanis, the leading researcher at the MRC Biostatistics Unit in Cambridge says:
"HIV remains an important public health problem. As long as a large number of people continue to be unaware of their condition, the infection will continue to pass from person to person. These findings highlight the need for continued public health policies aimed at both reducing further HIV transmission and encouraging individuals to get tested and access the help and services they need."
Study co-author Professor Noel Gill, head of the Health Protection Agency's HIV & STI department, said:
"The findings of this paper reveal the need to focus efforts on reducing transmission of HIV if we are to bring the overall number of cases down. Early diagnosis of HIV infection will give individuals access to treatment, improve their survival and reduce the risk of transmission to partners. The HPA recommends that people at higher risk of HIV, such as men who have sex with men, should test at least annually for HIV and that everyone should use a condom with all new or casual sexual partners - it is the surest way to ensure you do not become infected with a serious sexually transmitted infection such as HIV."
How they did it: triangulating data
The researchers estimated trends in diagnosed and undiagnosed HIV prevalence by putting together different sets of data. They used data on exposure group sizes from behavioural surveys and the population census; on prevalence of total and undiagnosed infection and proportions of infections diagnosed from unlinked anonymous sero-prevalence surveys and community surveys; and on the total number diagnosed from an annual survey of individuals with diagnosed HIV infection. They put these different data together, using a form of statistical "triangulation" of the available data, known as Bayesian multi-parameter evidence synthesis.
Source Medical Research Council
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