Changes

Just how distinct is a zoonosis from a non-zoonosis? The exploration of this question which I find most fascinating is that of HIV; molecular phylogeny generally shows that if one goes far back enough, what may affect only one species today might actually have made the leap from one animal to another further back in time. The human immunodeficiency virus – which was first written about in ''Morbidity and Mortality Weekly Report'', then went through a series of name changes – is being shown to have more definitive roots in SIV, the equivalent which affects other primates. The widely circulated Cut-Hunter explanation (in which it is supposed that a hunter somewhere in Central Africa killed an infected chimpanzee, and may have cut himself) represents a small part of the story, according to some. The observed twelve subtypes of HIV even suggest to some that there were ''at least'' twelve spillovers of HIV into human beings!

Stretching into the past, and reaching into the future, Quammen has done a splendid job at illuminating the tale of zoonoses and writing of the animals, unsuspecting societies and tenacious researchers involved. It points to the possibility that a zoonosis would be included in the chain of the Next Big Ones, succeeding the bubonic plague, smallpox, 1918-1919 influenza pandemic, and HIV/AIDS. More importantly, while Quammen doesn’t state that we humans are exclusively responsible for the crossing over of animal diseases, one is as a reader reminded yet again of just how unisolated we are from nature.