The scientific advances and the programs that have been developed over just the last few years now provide an historic opportunity to drive HIV to levels that we had previously not dared to hope for. There is a confluence of four forces that are working to make this happen: compelling evidence for the power of the interventions we deliver, falling costs, experience in getting the results we need and a revolution in our understanding of the epidemic. This means that we can direct, with pinpoint accuracy, interventions that work and are affordable, to those whose lives are threatened by one of the biggest causes of lost health in the world.
The advancement of therapeutics for HIV in recent years has captured the imagination of the world. Antiretrovirals really are the medicines that keep on giving: not only do they keep HIV-infected people alive for about as long as uninfected people under optimal conditions; they provide a two-pronged approach to cutting the spread of HIV by making HIV-infected patients dramatically less infectious and uninfected people less susceptible to infection. If properly harnessed, this could drive HIV infections down by at least 50 percent. Indeed, in South Africa a recent study suggests that treatment is already having a large impact by reducing risk of infection by more than 30 percent.
Remarkably, at the very time that we began to discover the added benefits of HIV medicine, the cost of the drugs started tumbling. The cost of the preferred set of antiretrovirals has fallen by 70 percent since 2007. We know that drugs on their own can't save lives -- you need procurement processes, supply chains, and clinics. But the cost of those in relation to providing treatment has also been declining, as programs have "learnt by doing" -- by, on average, about 10 percent every year. These two forces -- greater benefits and lower costs -- mean that the "health per dollar" gained by these interventions is higher than it has even been before.
Other interventions are also having an increasing impact as our knowledge grows with experience. We showed that male circumcision may reduce a man's chance of infection by as much as 60 percent, and new approaches to generate demand are gaining traction. New medical devices may further increase uptake by liberating the procedure from the necessity for aseptic conditions and rare surgeons. Changes in sexual behavior have also taken hold in many countries and have been responsible for the largest declines in epidemics we have seen to date -- in Uganda, Thailand, Zimbabwe, South Africa, Malawi, and the list is increasing. "Bottling" the behavior change into an intervention has been a challenge, but in specific populations where the motivation is there -- such as where one partner in a marriage is infected and the other is not -- we are seeing signs that informing couples of the risk can lead to increased use of condoms, which reduces the risk of infection significantly.
These interventions, however, would be misdirected and used inefficiently if we did not understand what drives the HIV epidemic. Fortunately, we know more about the epidemic today than ever before and the insights we are gaining present major opportunities to sharpen the impact of our interventions. HIV isn't 'like flu', which can wash over an entire population and leave almost everyone infected. Instead, HIV spreads through intimate relationships that tend to be formed locally and its spread can be eased by practices and traditions that are specific to communities. So, in many settings HIV exists in clumps -- or hot spots -- amid a sea of much lower levels of infection. For instance, in Kenya the risk of infection can vary tenfold from one county to the next. In fact, there are hotspots within hotspots. Within the highest prevalence corner of South Africa, a study has found that up to a third of infections may occur within just 6 percent of the area. And, within those hotspots, we see that the risk of infection is piled upon specific small groups -- especially young women, sex workers, and those with long-term partners who are positive. Now that we have the tools and resources, we can leverage this new intelligence to squeeze even more impact out of the resources we have. Our computer models suggest that impact could increase by 20 percent, just by redirecting the same resources to the populations at greatest risk of infection and transmission.
A 20 percent efficiency gain in any field is a reason to double-down an investment. But, infectious diseases behave differently to investment in other sectors. First, they can bounce back if the pressure we have applied to them is released, even for a moment. Second, the economics of HIV interventions mean that, as we are beginning to see downturns in infection levels, now is the time to invest: the interventions we need would not be possible if we returned to phase of rapid epidemic growth. Finally, the impact that we now think we can achieve would make the epidemic much more fragile -- so that an additional intervention could be the fatal blow. Scientific investigation into possible new forms of antiretrovirals for preventing infections and vaccines are continuing at a rapid pace, and no one would bet against further breakthroughs. Investment now -- in the right interventions for the right populations at the right time -- would save millions of lives, but also "soften" the epidemic and give the goal of the AIDS-Free Generation compelling scientific backing.