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The impact of undiagnosed infection on HIV transmission

Reducing undiagnosed infection is vital because an individual can only take HIV treatment if HIV has been diagnosed. Effective HIV treatment reduces HIV viral load, the main biological predictor of the risk of HIV transmission. UK treatment guidelines state that people with CD4 counts above 350 cells/mm3 should be allowed to choose to start treatment in order to reduce their risk of passing on HIV to sexual partners. People who remain undiagnosed – and their partners – are unable to benefit from this recommendation.

UK studies suggest that undiagnosed infection is a major contribution to the spread of HIV in MSM. A national study found that one third of MSM living with HIV are infectious, with a viral load above 1500 copies/ml. However, the majority (62%) of these men are undiagnosed. A modelling study estimated that, in 2010, 48% of new infections were acquired from men with undiagnosed primary HIV infection, 34% from men with undiagnosed chronic infection, 10% from men who were diagnosed but not on treatment, and 7% from men on treatment. High rates of partner change are likely to amplify the impact of undiagnosed infection.

Similar estimates are not available for African people in the UK.

Undiagnosed HIV infection

Published November 2013

Last reviewed November 2013

Next review November 2016

This content was checked for accuracy at the time it was written. It may have been superseded by more recent developments. NAM recommends checking whether this is the most current information when making decisions that may affect your health.
Community Consensus Statement on Access to HIV Treatment and its Use for Prevention

Together, we can make it happen

We can end HIV soon if people have equal access to HIV drugs as treatment and as PrEP, and have free choice over whether to take them.

Launched today, the Community Consensus Statement is a basic set of principles aimed at making sure that happens.

The Community Consensus Statement is a joint initiative of AVAC, EATG, MSMGF, GNP+, HIV i-Base, the International HIV/AIDS Alliance, ITPC and NAM/aidsmap
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This content was checked for accuracy at the time it was written. It may have been superseded by more recent developments. NAM recommends checking whether this is the most current information when making decisions that may affect your health.

NAM’s information is intended to support, rather than replace, consultation with a healthcare professional. Talk to your doctor or another member of your healthcare team for advice tailored to your situation.