Spillover: Animal Infections and the Next Human Pandemic

Abstract

Spillover is impressive in examining the historical spread of zoonosis and its implications for human beings. Defining “spillover” as an event in which “the pathogen passes from members of one species, as host, into members of another,” David Quammen, the author of works of environmental journalism such as The Song of the Dodo (1996) and Monster of God (2004), traces the ecological and epidemiological background of such diseases, including Ebola, SARS, and AIDS (43). For each of these diseases, Quammen explores how it jumps to human populations, the effects it brings, and how it has been discovered and studied. Spillover focuses on three aspects of the interplay between human beings and animals. First, Quammen clarifies the underlying mechanisms of zoonosis. Nature itself is teeming with microbes, and animals and microbes have established dependent and mutually beneficial relationships within their habitats. However, human intervention has contributed to the disintegration of ecosystems at a cataclysmic rate. Clearing forests, slaughtering animals, running off nutrients into the oceans, and other “civilizing” incursions upon natural landscapes, which host a vast reservoir of microbes, compel many microbes to use human beings as hosts in these newly “civilized” environments. Second, Quammen argues that it is difficult to detect and prevent zoonosis because viruses do not swim or crawl around but hide silently and wait for opportunities to jump or mutate. This intrinsic hiding feature, when combined with crowded populations, can have catastrophic consequences. Finally, Quammen argues that the AIDS, Ebola, and SARS outbreaks were not discrete or anomalous incidents; unexpected outbreaks throughout history implicitly point to the gruesome prospect that human beings will suffer new and perhaps even more severe diseases if they continue their usual mismanagement of nature and neglect the spillover phenomenon.