HIV acquisition and HIV transmission through sexual intercourse are two very different things. The former relates to an HIV negative individual being infected by an HIV positive person whilst the later is about an HIV positive individual infecting an HIV negative person.

That may seems obvious or hair splitting, but when it comes to ending the spread of HIV in the population, it is very important to understand the difference between HIV acquisition and HIV transmission.

HIV acquisition can be regarded as a dynamic and active process in the person exposed to HIV. Not all unprotected sex acts lead to HIV acquisition. Many factors contribute to the person exposed to HIV becoming infected. Some of the factors that will decide the fate of the HIV virus include the nature and type of the sex act, the amount and type of virus the person is exposed to, its immunological status, the existence of conditions favouring acquisition (epithelium irritation or fragility, other STIs), some genetic factors providing resistance or facilitating infection.

Targeting acquisition at the recipient level implies using either a mechanical or chemical device that act as a barrier between the infected biological fluid (semen) and the uninfected host, or a combination of interventions (STI treatment, Healthy life style…) that cannot address all the relevant factors leading to the uninfected person becoming infected.

STI treatment, microbicides and PrEP are typical approaches addressing acquisition by the recipient, i.e. they are targeting HIV negative people. Remarkably, PrEP has no effect on STI and more importantly, there is no proof that preventive ARV treatment of an HIV negative individual with ARV can prevent acquisition of HIV. Results of forthcoming clinical trials may change this but so far, there is no data available in human. Microbicides, with or without ARV have so far failed to prevent acquisition. Treatment of STI in the host has also been inconclusive to reduce acquisition.

Conversely, HIV transmission depends on only one factor: that the HIV virus leaves the body of the HIV infected person to enter the body of an uninfected person. Stopping HIV transmission can be reduced to stopping HIV travelling from the infected to the uninfected.

Condoms are a typical approach to prevent transmission from an infected individual to an uninfected one.  Condoms also work to prevemt acquisition but only if used by the HIV infected person, which bring us back to preventing transmission. But ARV treatment can also work for preventing transmission. Unlike PrEP, there are evidences that treatment does prevent transmission. The use of ARV for the Prevention of Mother to Child Transmission (PMTCT) clearly shows that by giving ARV to the infected mother, which reduce the viral load in her blood, the risk of her transmitting HIV to her child is reduced. In fact, a recent study conducted in Denmark showed that not a single mother-to-child HIV transmission occurred in Denmark when the national treatment guidelines were followed (comment at AIDSMAP).

Beside understanding how each HIV prevention intervention targets either acquisition or transmission, it is important to bear in mind the number of people that need to be targeted by the intervention. Interventions that target acquisition require targeting many more people (HIV negative) than interventions that target transmission (HIV positive). Interventions targeting transmission are expected to be more focused, cheaper, and more efficacious. And number means cost, infrastructure, personnel needed to deliver the intervention.

Of course, there is the threat of building stigma by targeting preferentially HIV positive people. But let’s look at what has happened with HIV testing and how attitudes to testing have changed. Before HAART, testing was taboo. People were not encouraged to test. It was stigmatising to ask people to test. Such attitude was understandable to some extent as there was not much hope when HIV positive in the early 90’s. A few years after HAART became available in the late 90′s and it was all about “knowing your status!” It is amazing how advocacy and CBO’s attitude has changed and how they have come about the idea that testing is actually a good thing.

There is a lot of stigma still attached to HIV and addressing sigma requires recognizing that some of it is generated by our attitude toward HIV (Stigma is a complex issue outside the point of this post). This stigma contributed to a very different of the HIV epidemics by Public Health authorities compared to what would have been done in a different time and place. We don’t wait for people to develop TB before treating them; we conduct systematic screening for TB infection. We don’t wait years before treating women with breast cancer once diagnosed; we treat them as soon as possible. But when it comes to HIV… “Tut tut! It’s HIV, can’t do that, better not knowing and better wait until treatment is really needed… live and let die.”

In twenty or thirty years from now, we may be looking back at what we are currently doing and say, “We had the means to diagnose the infection, we had the means to treat infected people, we had the means to cut down transmission, we had the means to save life and what did we do?”

So, what shall we do? Procrastinate for another decade or start acting now?

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