ABSTRACT
The acceleration of international travel and the growth of global commerce are making the rapid spread of infectious diseases a much more pressing security challenge. In a remote part of southern China in late 2002, a new respiratory disease that became known as severe acute respiratory syndrome (SARS) jumped from animals to people and quickly spread to other parts of the country. Measured in numbers of premature deaths and associated physical suffering, the biggest source of human insecurity, past and present, is the dreaded Fourth Horseman of the Apocalypse—infectious disease. Research and surveillance are now yielding a much better understanding of the dynamics of disease outbreaks. Large-scale disease outbreaks, epidemics, and even pandemics occur when something happens to disturb an evolutionary equilibrium that normally exists between people and pathogens. Technological innovation is also linked to many environmental changes that are helping new diseases emerge and old ones resurface and spread.
