We've been lucky. The avian influenza (H5N1) virus that first emerged in Hong Kong in 1997 -- which killed six and caused 18 serious illnesses -- has not acquired the ability to spread easily from person to person. Virtually all of the reported cases have involved contact with infected birds or bird products. Thus the outbreak required the depopulation of all the chicken farms and poultry markets in the region -- no small project -- in order to stop the outbreak from spreading.
The virus resurfaced in 2003 and, since then, has killed 339 out of 576 infected people PDF, making it an astonishingly deadly microbe with an estimated mortality rate of around 60 percent. To put this into perspective, the 1918 influenza virus, which killed somewhere between 50 to 100 million people worldwide, had a mortality rate between 2 to 3 percent. And most influenza epidemics typically have mortality rates less than 0.1 percent.
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