In the post-cold war era, new amorphous challenges to national and international security have emerged. These threats do not stem from the actions of clearly defined individual states but from diffuse issues that transcend sovereign borders and bear directly off the the effects of increasing globalization. Such "gray area" phenomena are redefining the nature and understanding of global stability, challenging policymakers to develop new, non-state -centered paradigms of security. This report focuses specifically on the threat posed by new and reemerging infectious diseases, providing a more comprehensive analysis of the security implications posed by pathogenic microorganisms than has been done to date. The study examines the impact of the HIV/AIDS epidemic in South Africa, highlighting this particular crisis as a graphic example of the devastating effects that infectious disease can have on virtually every aspect of a state's functioning viability. It also makes a detailed analysis of the United States, delineating the threat posed by specific diseases, assessing the effectiveness of the existing public health infrastructure, and offering specific actions that can be taken to improve the country's ability to meet this emerging challenge.