Human culture, ecological change, and infectious disease: Are weexperiencing history's fourth great transition?

摘要

Infection is intrinsic to life on earth. The bacteria, viruses, protozoa and other infectious agents intend no harm to the infected individual. Their interests are, as for all other species, finding a way of obtaining nutrients, and energy and of reproducing. They and their predecessors have long experience, over several billion years, of making a living in this way. Most infection is benign, some is beneficial to both host and microbe (called "symbiosis"), and some adversely affects the host's biology. It is only that last category that we call "infectious disease." During the long narrative of human cultural evolution, of population dispersal around the world, and of subsequent inter-population contact and conflict there have been several distinct transitions in the relationships of Homo sapiens with the natural world. Each of these transitions in human ecology and in inter-population interaction has profoundly changed the patterns of infectious disease. These, in turn, have often affected the course of history (McMichael 2001). Today, we may be living through another of these great transitional periods. There is much discussion about the "emergence and resurgence" of infectious diseases, particularly in relation to the many and extensive ongoing disruptions of the world's ecosystems (Epstein 1998; Rapport et al. 1998; McMichael & Bouma 2000). An unusually large number of new infectious diseases seem to have been identified in the past quarter-century. This includes the spectacular emergence and spread of HIV/AIDS and the somewhat mysterious occurrence of "mad cow disease" and its human equivalent, variant Creutzfeldt-Jakob Disease (Donnelly et al. 1999). Patterns of land-use--forest clearance, irrigation, and intensive agTiculture--have engendered various new infectious agents, including several hemorrhagic fever viruses in Latin America (Morse 1995). Various old infectious diseases such as malaria, cholera, diphtheria, dengue fever, and tuberculosis, along with antibiotic-resistant forms of many such diseases, have been on the increase in recent times. Do we simply know much more today about the world's diverse and ever-changing infectious diseases-or is an actual "shift" of some kind occurring in the equilibrium point between humans and microbes?