In winter 2002, the deadly SARS virus emerged unnoticed in a rapidly developing region of Southern China, spread quickly to the cosmopolitan city of Hong Kong, then on to Southeast Asia and as far as Cambodia.
Almost immediately, airline passengers transmitted it to several nations, including Singapore and Canada, two of the world's most prosperous and highly developed nations.
A spate of sudden deaths, the sight of well-to-do travelers fleeing in surgical masks, and the subsequent economic impact of an international quarantine reminded the world that infectious diseases are oblivious to political boundaries. They emerge locally, but spread globally and, along the way, become increasingly harder to contain.
Global health requires that the world's citizens collaborate to improve public health services in all nations, rich or poor, and stop disease outbreaks at their source.