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Luc Montagnier is a distinguished virologist at the Pasteur Institute, Paris, who has been at the forefront of one of the most exciting scientific detective stories of the 20th century. He was among the first to realise that an utterly new kind of virus was responsible for the greatest and most intractable plague of recent times, the Aids epidemic.

He has also been embroiled in a fierce controversy, one that is symptomatic of the intense competitiveness of present-day science. There is apparently good molecular evidence that his laboratory was the first to isolate HIV-1, the more dangerous of the two Aids viruses. And it is also very likely that his research group was the first to recognise just how unique this virus is. But the story is by no means clear. A rival group, led by Robert Gallo in the United States, had earlier been the first to find an HIV-like virus in humans, one that causes cancer. And it, too, had the capability of isolating and analysing the Aids virus. Unfortunately, because of a sequence of events that will probably remain a mystery, the virus that Gallo's group did isolate and analyse happened to be the one that was the same as from Montagnier's lab, and indeed was one that Montagnier was working on simultaneously.

The two groups were working in parallel, at breakneck speed. Several strains of the virus were being grown on both sides of the Atlantic. The most likely explanation seems to have been an unfortunate cross-contamination between cell lines that took place in the Gallo lab. But regardless of the sequence of events, both sides were furious and aggrieved. Gallo was acquitted of wrong-doing by a panel of the US National Institutes of Health, although he was criticised by the panel for the way he had run his lab during the critical period. And an agreement was hammered out - signed on both sides with clenched teeth - that named Montagnier and Gallo co-discoverers of the virus.

One consequence of the virus mix-up and the subsequent bitter argument has been that Montagnier and Gallo are very unlikely to get the Nobel prize for their discovery. This is a shame, because the science involved in the discovery, and the science that has been done since that time that has increased our understanding of the virus, is truly ground-breaking. The Aids virus is not an "easy" pathogen, one that can be simply streaked out on a Petri dish and examined under a microscope. It is a much subtler foe.

Viruses have been some of our most stubborn enemies. Invisible under the light microscope, passing through bacteriological filters with ease, they can be grown only in the cells of their hosts. But most of them do have some properties in common with disease-causing bacteria. The viruses that cause smallpox, polio and yellow fever multiply readily to huge and easily detectable numbers in their host cells. They cause obvious symptoms in their victims. And their genes stay much the same from one generation to the next, so that it is possible to devise vaccines against them.

None of this is true with the viruses that cause Aids. These viruses multiply only in particular cells of the immune system, and they can remain "latent" for long periods by inserting themselves into the chromosomes of their hosts and hiding there. The worst initial symptom that they cause is something like the flu, and it is only years later that the damage that they do to the immune system lays their victims open to a bewildering variety of opportunistic diseases.

To confuse the picture further, these diseases that actually kill the Aids victims differ from one part of the world (and even one socioeconomic class) to another. And to make things worse, the Aids viruses mutate so rapidly that it has so far been impossible to devise a satisfactory vaccine.

In the first part of his book, Montagnier recounts the excitement and frustration of tracking down the virus. One fascinating story, new to me, was about his rush to get a paper ready for a meeting in the US about his early characterisation of the virus. He was so pressed for time that he asked Gallo, the organiser of the meeting, to write the summary of his paper. According to Montagnier, Gallo's summary implied that the Aids virus was very similar to the cancer-causing virus that Gallo had found earlier, even though by this time Montagnier was growing more certain that the two viruses were in fact very different. It was unfortunate interactions such as this that led to the growing animosity between Montagnier and Gallo.

The story Montagnier recounts in this part of the book is exciting, well told and very much from his point of view. The last two-thirds of the book are less successful. He turns to what is known about the virus, its spread in the third world and what can be done about the epidemic scientifically and politically. He also raises the possibility that poorly understood organisms called mycoplasmas might work in tandem with the virus and enhance its effects. Unfortunately, the book was originally published in French in 1994 and is much dated as a result.

There are attempts to bring the book up to date, by including discussions of the (very expensive) protease inhibitors and other drugs that have helped to ameliorate the disease in the first world. But there are odd gaps. For example, Montagnier states that nothing is known about genes for resistance to the virus, when in fact there is now excellent evidence that some people carry mutant receptor proteins on the surface of their cells that can confer resistance by preventing the virus from being taken up.

The book, unavoidably, ends on a gloomy note. The virus continues to spread in sub-Saharan Africa and in South and Southeast Asia, virtually unchecked. The intractable nature of the disease and its sexual mode of transmission, combined with its long latent period, are compounded by the fact that Aids contributes to the spread of other dangerous diseases such as tuberculosis. The politics of denial and ignorance, along with the widespread subjugation of women in countries where Aids is most prevalent, yields a deadly mix that will make this epidemic one of the great problems facing us in this century. Montagnier has combined brilliant science and hard work to reveal the full dimensions of the problem. It is up to science and society to solve it.

Christopher Wills is professor of biology, University of California, San Diego.