Martin W

Article by Carl Zimmer – TAMING PATHOGENS: AN ELEGANT IDEA, BUT WILL IT WORK? – mentions some criticisms of evolutionary biology and pathogens, but doesn’t seem they are by any means watertight. Includes:

Ewald complains … the critics … leave out a crucial component of his work, for example, the mode by which a disease infects new hosts. If hosts become so sick they can’t move, a parasite can only infect other people who come close, unless a vector such as a mosquito can transport it. This factor is crucial in Ewald’s explanation of Spanish flu. … "My argument was that at the Western Front you had conditions in which people who were completely immobilized could contact hundreds or thousands of people." Sick soldiers were moved on stretchers to triage areas, then to makeshift hospitals, then onto crowded trains. In these conditions, a flu virus could devastate its host but still infect vast numbers of people. "My argument was that we wouldn’t see a 1918 pandemic arise unless we duplicated this situation which occurred on the Western Front," says Ewald.

– relevant to birds, too. Poultry farms can become "disease factories" (as Wendy Orent puts it); but in the wild, bird flus are mild, because Dead Ducks Don’t Fly.