SARS, avian influenza and swine flu are the first new diseases of the twenty-first century. They are all diseases of globalization, or diseases of modernity, and while relatively limited in their impact, they have offered dress-rehearsals for future epidemics. As information about SARS spread internationally in 2002, in spite of China's campaign of silence, the global response had a curiously twofold character: on one hand, the mobilization of biologists and epidemiologists across national frontiers was rapid and unprecedented, while on the other hand, public health strategies on the ground were largely familiar from previous eras. If the spread of information and collaboration on international health regulations have been two positive aspects of public health response in the first decade of this century, more worrying questions have been raised concerning the production and distribution of drugs and the capacity of for-profit healthcare systems to cope with a major epidemic.