IN 1997, Lam Hoi-Ka, a previously healthy three-year-old boy, died of multiple organ failure in Hong Kong. When a team of virologists from the Netherlands declared that the death-dealing agent had been H5N1, a virus that was previously known to infect only birds, scientists were shocked. The theoretical possibility of a deadly global pandemic, similar to the 1918 flu that killed millions of people, was suddenly made real.