Outbreaks of avian and swine flu have reawakened fears that had lain dormant for nearly a century, ever since the influenza pandemic of 1918 that killed at least 50 million people worldwide. When a highly lethal strain of avian flu broke out in Asia in recent years and raced westward, the Washington Post’s Alan Sipress chased the emerging threat as it infiltrated remote jungle villages, mountain redoubts, and teeming cities. He tracked the virus across nine countries, watching its secrets repeatedly elude the world’s brightest scientists and most intrepid disease hunters. Savage and mercurial, this novel influenza strain—H5N1—has been called the kissing cousin of the Spanish flu and, with just a few genetic tweaks, could kill millions of people. None of us is immune. The Fatal Strain is a fast-moving account that weaves cultural, political, and scientific strands into a tale of inevitable epidemic. In his vivid portrayal of the struggle between man and microbe, Sipress chronicles the accelerating number of near misses and explores the cruel dynamic that has often made Asia the fountainhead of killer flu strains. Even more than modern medicine, it is chicken smugglers, fighting cock breeders, and witch doctors who could determine the evolution of this viral menace by allowing it to breed and speeding it on its way. The ease of international travel and the delicate balance of today’s global economy have left the world vulnerable to pandemic in a way the victims of 1918 could never imagine. But it is human failings that may pose the greatest peril. Political bosses in country after country have covered up outbreaks. Ancient customs, like trading in live poultry and the ritual release of birds to earn religious merit, have failed to adapt to the microbial threat. The world’s wealthy countries have left poorer, frontline countries without affordable vaccines or other weapons for confronting the disease, fostering a sense of grievance that endangers us all. The chilling truth is that we don’t have command over the H5N1 virus. It continues to spread, thwarting efforts to uproot it. And as it does, the viral dice continue to roll, threatening to produce a pandemic strain that is both deadly and can spread as easily as the common cold. Swine flu has reminded us that flu epidemics happen. Sipress reminds us something far worse could be brewing.