Aids is the first postmodern plague, its brief history marked by horror stories and conspiracy theories. Among my favourite is the ridiculous suggestion that the disease was created by the CIA for biological warfare. A more tenable suggestion - Edward Hooper's - is that the epidemic may have been started accidentally by scientists while developing vaccines against polio.
At the start of the 1980s, we in the west complacently believed that infectious disease had sunk into history. Until, that is, the American Centres of Disease Control began noticing that clusters of homosexual men were contracting a bizarre menagerie of infectious agents. Investigations showed that the immune system, which usually deters microbial intruders with impunity, had virtually disappeared from these men. What had caused this disappearance? The wise money was on another microbe, possibly a virus, and a frantic contest to find its identity ensued. Luc Montagnier, at the Pasteur Institute in Paris, first isolated the human immunodeficiency virus (HIV) which is responsible for the disease. (The lobby, disgracefully championed by Andrew Neil at the Sunday Times, which claimed that Aids is not caused by a virus, is now discredited.)
Montagnier's victory was, however, tainted by rivals competing in the hunt for scientific glory. Robert Gallo led American efforts, and has since been cited as a co-discoverer in a Franco-American agreement ratified by Jacques Chirac and Ronald Reagan, which continues to vex Montagnier. In his autobiographical account of the race to discover the virus, the circumspect Montagnier can barely contain his bitterness at the outcome. He takes sideswipes, not just at what he sees as Gallo's opportunism and inadequate science, but also generally at the scientific establishment.
HIV invades the command centre of the immune system, comprised of "helper T cells", and eventually kills them. The continuous production of these cells means that it can take as long as a decade before the virus depletes the immune system sufficiently to expose the body to the plethora of opportunistic infections which end up killing the afflicted.
The origin of HIV has remained a mystery - which goes some way to explain why CIA-style conspiracies arise. It's true that some monkeys possess viruses similar to HIV, and many investigators agree that such a virus was transferred to humans somewhere in Africa in the late 1950s. Montagnier glosses over the details of this calamitous leap. Perhaps indigenous tribesmen caught the disease through eating chimpanzee meat. Perhaps a playful scratch from a pet monkey was enough to cause the transfer. Other hypotheses, such as that expounded by Charles Gilks at Oxford University, that suggest that the virus was transmitted directly from chimpanzee blood in early experiments on possible malaria vaccines, have as much biological plausibility as the polio link.
Whatever the cause, good science should be published in specialist journals after detailed scrutiny by several experts in the field. This process of peer review evolved specifically to weed out sensationalist speculation from any old Tom, Dick or Edward Hooper.
The system does contain flaws. New ideas are often neglected through misunderstandings or even for less scrupulous reasons. Montagnier himself suffered at the hands of competitors refereeing his work, and every small-time scientist has a conspiracy theory to peddle about a rejected manuscript. In spite of the flaws, however, a better system to ensure that the scientific juggernaut rumbles onward has yet to be devised.
Regardless of the bridging event which brought HIV into humans, another important question remains. How did a major Aids epidemic develop among gays in the USA in the 1980s? The modern shift in sexual behaviour, particularly among homosexuals, is often cited as a key contributory factor. Promiscuity and anal sex may not be a particularly modern invention, but Oscar Wilde and even Joe Orton would surely have blushed at some of the scenes enacted in the New York bathhouses.
Montagnier doubts that such behaviour in such places could alone have been responsible for the epidemic. He believes that other microbes emerged as co-factors promoting the survival of HIV, which succeeds better in individuals already carrying other infections, because they have more activated immune cells to harbour the virus when it enters. This multi-infection link may also explain the enormous prevalence of HIV in Africa.
Recent advances in treating the disease mean that triple combination therapy can keep the virus in check for many years, if not yet eliminate it. Further advances are expected. Vaccines have proven slow in coming, although there is some optimism that a breakthrough may not be far away. Even with these advances, however, it must be remembered that effective treatment for other infections such as malaria and tuberculosis has been available for more than half a century. And yet more people around the world die of these diseases than ever before. Five per cent of the world's HIV-infected population receive therapy. The others are unable to afford treatment. Hard economics, not science, will dominate the final outcome of the global Aids epidemic.
Mike Barrett is a lecturer at the Institute of Biomedical and Life Sciences at Glasgow University