Another sort of Asian contagion

“WHEN Hong Kong sneezes, the world catches cold.” Pray this is just a financial metaphor. Every day brings scarier news of an influenza virus in Hong Kong that has killed two people and infected seven more. New variants of the most common influenza virus are nothing unusual: it constantly mutates. But this virus, called H5N1, is entirely new, the first known to have jumped directly from birds (chickens in this case) to humans, without another species in between. And this is why it is frightening: humans have not been exposed to anything sufficiently like it to build up natural immunity.