Data on the genetic sequences of the H5N1 infections that had been identified in 2005 showed that this particular strain was mutating in ways that could make it more menacing to people.10 It was believed that the H5N1 virus had first jumped from birds to humans in Hong Kong in 1997, in an outbreak that infected eighteen people, six of whom would die.11 The infection was fearsome, causing severe inflammation of the lungs, a condition known as pneumonitis.12 When it first emerged, people were stricken only after close contact with infected chickens; there was no evidence of person-to-person
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