TWO things that can make humanity break out in a cold sweat: things too small to see and things too big to comprehend. In that sense, viruses are on the same footing as God: unseeable, capricious, feral and almost omnipotent.

When the AIDS virus began its slow burn from Central Africa and girdled the globe, it was considered the ultimate killing machine: like all viruses, neither living nor dead, probably soulless (all organised religions would have problems categorising them), capable of sleeping with motors idling for years, horrendously fecund, 100 per cent fatal.

Till the Marburg and the Ebola viruses exploded upon an unsuspecting world a decade and a half ago. Soon enough, it became evident to doctors and biogeneticists in the West that they were dealing with 2 viruses so powerful that they had nothing at hand to combat them with. Nothing. The Marburg virus is 50 per cent fatal, Ebola 90 per cent. And on a scale of agony of 1 to 10, AIDS would be 4, Marburg and Ebola would bust out of the chart.

Do readers wish to know of this agony? If The Hot Zone were a work of Transylvannian fiction, Richard Preston would be a worthy successor to Stephen King. But he is a science journalist with a fair pen: when he documents with clinical detail of Marburg and Ebola "sloughing off" the internal organs of the body and the victim "crashing and bleeding out" in 5 days of haemorrhaging from every orifice and going psychotic with a shortcircuited brain, it's difficult not to think of the best, or the worst, of Hollywood horror.

This book is all gore, 100 million American Psychos in the fullstop at the end of this sentence. Preston is a student of the New Journalism -- old journalism by now -- and this book is retro writing at its best. What he misses out is probably what is of little importance to Western science journalists but of violent interest to the Third World: the nasty global politics of disease biogenetics, first dissected by Dominique Lapierre in his book on AIDS, End of Love.

Africa is heart of darkness all over again. In many ways, the slew of books (Laurie Garrett's The Coming Plague among them) on AIDS and other viruses return to Africa an unkind epithet it has tried hard to shrug off -- The Dark Continent. In many ways, again, it would have been better to call it the Last Frontier.