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Nipping HIV in the bud: could we use genotyping to interrupt transmission?
Gus Cairns, 2014-03-10 07:00:00

The Conference on Retroviruses and Opportunistic Infections (CROI) this year heard a number of presentations on phylogenetic analysis – the use of genetic fingerprinting of HIV to trace patterns of transmission and prioritise groups for targeting prevention.

If we take a sample of the genetic make-up of the virus of everyone diagnosed with HIV in a certain area and compare them, we can identify clusters or chains of infection, because recently transmitted viruses are almost identical in the person who has passed on HIV (the 'transmitter') and the person who has acquired it (the 'recipient'). The viruses will also be closely similar in people who are not such a ‘transmission pair’ but who acquired HIV from the same person or who form part of a cluster of infections. People within a cluster can then be prioritised for early HIV therapy, help with risk-reduction, and for contact-tracing of their undiagnosed or still HIV-negative contacts.

Concerns about identifying and criminalising the transmitter have tended to make both physicians and patient advocates wary of using this tool, phylogenetic analysis. However, in the situation of continuing high-incidence epidemics in men who have sex with men, it could be used to interrupt chains of transmission. Prioritising someone connected to a large number of other partners for antiretroviral therapy (ART) could have a disproportionate influence in reducing community incidence compared with treating people according to presentation time or CD4 criteria. It is also a way, if resources to treat everyone with HIV are stretched, of more efficiently using ART to prevent ongoing infection.