“If you look at the world from the point of view of a hungry virus,” the historian William H. McNeill has noted, “or even a bacterium – we offer a magnificent feeding ground with all our billions of human bodies, where, in the very recent past, there were only half as many people. In some 25 or 27 years, we have doubled in number. A marvelous target for any organism that can adapt itself to invading us.”
