The HIV-AIDS epidemic is unprecedented for a number of reasons.
First, who can remember another disease that arose as quickly as HIV did in the early 1980s to infect millions of people around the world, almost all of whom succumbed to their illnesses at a time when antiretroviral drugs were non-available?
Second, the development of safe and well-tolerated ARVs over the past 25 years has now resulted in a situation in which almost all of these people can aspire to live for many years, as HIV has been transformed into a chronic, manageable condition. Of course, many problems remain, not the least of which is that HIV continues to spread to millions more people each year. In addition, people who live in developing countries are often treated with inferior drugs and so are less likely to fully benefit from these treatment advances.
All this notwithstanding, there is now a widespread consensus that the only truly effective way to deal with the HIV epidemic over the long term will be to find a cure. Although global programs to provide ARVs to people in developing countries (who could not otherwise afford them) have been successful, they may well be unsustainable over the long term. Simply put, the total costs may well exceed hundreds of billions of dollars over the next decade, and many health-care economists have sounded the alarm that the West may not be able to provide this assistance unless the global economy improves. Anyway, it is no panacea for anyone to have to take drugs every day for a lifetime.
So far, at least, the quest for an effective HIV vaccine has fallen flat, despite valiant and insightful efforts by scientists around the world. But there is palpable optimism about potential curative strategies.
Among other considerations, we now possess a much fuller understanding of the problems involved and recognize that HIV has been able to establish itself in latent form in long-lived cellular reservoirs that cannot be easily targeted by currently available ARVs. This has resulted in a large number of novel concepts aimed at reactivating these reservoirs, so that latently infected cells may be effectively targeted by more traditional drugs. In almost all Western countries, public and private granting agencies have now established dedicated funding programs to seek a cure. And for the first time, a large critical mass of scientists is fully engaged in this effort.
Research is also flourishing in a number of related areas. For example, the success of current ARV usage in the treatment of HIV has provided benefits to both society and individuals. We now know that people who are successfully treated have vastly diminished viral loads in their bodies and, as a consequence, are far less likely to transmit HIV than they otherwise would have been. On a population level, it has been shown that ARV use has led to significant reductions in community viral load, which refers to the average viral burden in a community of infected individuals.
Efforts are in place to protect against new infections (through the use of ARVs administered on a prophylactic basis) to people who might be at risk, in programs referred to as pre-exposure prophylaxis (PrEP). Some studies suggest that PrEP may be able to protect up to half of individuals at risk from acquiring HIV, so long as they take their ARVs as prescribed.
A related area of research, called Treatment as Prevention (TasP), holds that the successful mass use of ARVs will lead to diminished viral loads across populations, greatly reducing or halting the transmission of new HIV infections. Although concerns have been expressed that the development of HIV drug resistance and the transmission of drug-resistant viruses might thwart such efforts, the recent development of novel compounds that may not be as prone to drug resistance as earlier drugs may help to provide a solution to this problem.
We have more of a right to be optimistic today than at any time since the outbreak of the HIV epidemic.
Mark A. Wainberg is director of the McGill University AIDS Centre at the Jewish General Hospital in Montreal.
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