Introduction When contemplating the global architecture of contemporary security institutions, the World Health Organization (WHO) does not, perhaps understandably, readily spring to mind. The WHO was founded in 1948 to pursue the ‘attainment by all peoples of the highest possible level of health’, which was defined then as ‘a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity’. When the WHO was established as a specialised agency within the United Nations system, it was originally envisaged that the institution would serve as the world’ chief public health agency providing impartial, technical medical advice and direction to governments as, and when requested; and for more than sixty years the WHO has retained a strong public health profile performing this function. In more recent years, however, it has also adopted a much more explicit security agenda. Indeed, particularly since 2001 the WHO has been actively engaged in re-branding many of its traditional public health roles and functions as ‘global health security’, in addition to assuming a variety of new duties and responsibilities designed to counter well-established and newly emerging ‘threats’ to human health. Importantly, the WHO’ global health security agenda has been driven as much by its member states and real-world events as by its own institutional bureaucracy. Although legitimate questions remain as to who is benefitting most from this agenda, as this chapter reveals, several incidents in the early to mid-1990s generated new impetus amongst governments to develop more effective solutions to global health hazards. The WHO Secretariat, which was at that time confronting accusations of mismanagement, responded to this new demand by launching an extensive review of its disease outbreak policies and procedures. The need for enhanced response mechanisms was then further compounded by a series of naturally occurring and human-induced disease events towards the end of the twentieth century and first few years of the new century, notably including: the 1994 outbreak of plague in Surat, India; the 1995 outbreak of Ebola Haemorrhagic Fever in the former Zaire; the 2001 anthrax letter attacks in the United States; the 2003 Severe Acute Respiratory Syndrome (SARS) outbreak; and the progressive international spread of the H5N1 avian influenza virus from late 2003 onwards.