In this controversial book, the eminent biologist Paul W. Ewald offers some startling arguments:-Germs appear to be at the root of heart disease, Alzheimer s, schizophrenia, many forms of cancer, and other chronic diseases.-The greatest threats to our health come not from sensational killers such as Ebola, West Nile virus, and super-virulent strains of influenza, but from agents that are already h