The biggest conference yet on HIV/Aids was held this week. Thousands of delegates descended on Washington DC for the International Aids Conference (Aids 2012) to hear and see what is new by way of medical science, clinical guidelines, public-health policy, and not least of all, political discourse.

“Turning the tide together” is the official slogan of Aids 2012 – but what are the real issues? What do we know, and what do we need to learn, to make a crucial transition from this unrelenting disaster, to some sort of long-term management of HIV infection as a tolerable risk?

In essence there are two sides of the “intervention”, or “response” coin: treatment for those already infected, and prevention of new infections.

On the treatment side, antiretroviral (ARV) drugs are one of the astounding successes of modern science. No other comparably serious illness can be so thoroughly and successfully turned back, from even a very advanced stage.

However, treatment is not necessarily pleasant, and must be maintained consistently pretty much for the rest of the patient’s life. Although something to be concerned about, the danger of drug resistance developing in response to an occasional missed dose is often overplayed, and the process is usually technically misrepresented in mainstream discourse.

On the conventional prevention front there are numerous thrusts. The bruising search for an effective vaccine continues, while ARV drugs for HIV-free (yes, uninfected) high-risk people are investigated. The latter option seems to effectively prevent transmission when taken regularly, but it is a complex tale. This so-called “Pre-Exposure Prophylaxis” (or PrEP) already has a systemic (pill) and a topical (vaginal/rectal gel) incarnation.

There’s some excitement about recent reports linking a decrease in infection rates to modest “cash transfers”. These financial hand-outs help vulnerable individuals to manage their risk and to take part in education programmes. In some parts of the world, needle-exchange programmes also continue to feature in the mix.

The debate still rages on about messaging, and “non-biological” interventions generally. No one knows quite how people decide what risks to take.

Although behaviour patterns are always changing, it is still unclear how these changes might be positively influenced, if at all, without manipulation and condescension.

With literally thousands of updates on all these threads, the many stories, voices, debates and presentations from the conference could become the proverbial trees that obscure our view of the forest.

Meanwhile, the big shift of recent years, in thinking about both the social and biological approaches to the epidemic is the realisation that the two broad categories, of “treatment” and “prevention”, are inextricably linked. Treatment, in fact, is prevention, probably the most impressive form of prevention.

The simple fact has long been known, but has only recently formally been measured: a well-treated HIV-infected patient has a much lower chance of infecting others than an untreated person. The difference is so huge that it is barely possible for conventional clinical trials, following thousands of individuals, to reliably estimate the tiny residual infectiousness of well-treated patients whose virus is under control.

(Abstinence and condoms, we might note, are forms of risk management, and not actually interventions, but certainly they are effective.)

This holds vast implications for our established approach of treatment, in which patients “qualify” for ARV treatment only if their disease is sufficiently far advanced. The strategy arises from logistical and financial constraints, and was built around the arguably outdated experience of a previous generation of ARV regimens which had more frequent serious side effects, and were less consistently effective.

Reasons for delaying treatment are evaporating, as evidence pours in on the benefits of earlier treatment. A week or two before Aids 2012, the high-impact journal Plos-Medicine (free at ) dedicated a special edition to the impact of earlier treatment, as viewed through the lens of reduced infectiousness of the treated patients.

Although the details between various modelled scenarios vary greatly, under any reasonable assumptions the societal benefits of early treatment are substantial. A strong treatment policy, delivered by a generally strong health care system, offers the best hope yet of getting to a favourable tipping point, where HIV prevalence may be put into long- term remission.

Now that it is widely grasped that there is no real divide between treatment and prevention, discourse needs to shift so that the benefit of this deep synergy can be realised.

Many important and complex questions arise. Who comes for testing, and where, and how is it that many people still only find out they are infected after years of exposing multiple partners to risky sex? How does one offer treatment at ever earlier stages of disease, when the superficially apparent benefit, and hence the motivation to stick to the regimen, are less clear?

How easy is it to pay a huge up-front cost for long-term savings that only accrue beyond the technical planning horizon? How do we administer an audaciously bigger programme of drug distribution and chronic patient care than the already impressive one SA has set up in recent years? Are there effective, and ethical, ways of prioritising treatment access to key groups where the epidemiological impact will be more efficient?

There are, of course, also serious questions about the politics and sociology of making a big, expensive and complex effort to curb the impact of a sexually transmitted infection, and one which disproportionately affects already vulnerable populations.

One can only hope that these questions will be addressed as public discourse matures, and concern for the people and communities affected replaces defensive and moralistic posturing.

We will never really know the consequences of planned “interventions” until they unfold. However, there are enough impressive success stories in the HIV/Aids saga to show that optimism is rational, and that a unified approach to treatment and prevention offers genuine hope of a future in which HIV really is a retro virus of the past.

l Dr Alex Welte is the director of the SA Centre for Epidemiological Modelling and Analysis (Sacema) at Stellenbosch University. Sacema is a Department of Science and Technology / National Research Foundation Centre of Excellence. Readers can follow the conference atw