Severe acute respiratory syndrome (SARS) first emerged in Guangdong Province, China, in November 2002, and presented as an outbreak of a typical pneumonia that was soon recognized as a global threat. In Mainland China, it infected 5,327 people and caused 349 deaths within the first seven months of its recognition. In Hong Kong, SARS caused considerable disruption as this area faced the largest outbreak outside of Mainland China. It infected 1,755 people and caused 299 deaths (a fatality rate of 17.04%). Among the infected, 405 people (23.08%) were health care workers and medical students in hospitals and clinics. Within a month of recognition of this as a new type of infection, but before the disease pathogen was identified, it had spread to thirty-three countries and regions over the world, largely as a result of international air travel.

Although the number of worldwide cases remained relatively low (8,098 cases), the mortality rate (774 deaths) remained relatively high until July 7, 2003. This rate resulted in widespread concern, sometimes to the point of panic, in both affected and nonaffected populations. It was viewed in the same category as acquired immunodeficiency syndrome (AIDS) – a severe and readily transmissible new disease to emerge in the twenty-first century.

The SARS epidemic highlighted the need for a rapid international response to disease control. The recent outbreak of H5N1 influenza in birds in Southeast Asia has only reinforced the potential for a pandemic spread of newly emerging or evolving infectious agents.