The challenge of emerging and re-emerging infectious diseases

摘要

Infectious diseases have for centuries ranked with wars and famine as major challenges to human progress and survival. They remain among the leading causes of death and disability worldwide. Against a constant background of established infections, epidemics of new and old infectious diseases periodically emerge, greatly magnifying the global burden of infections. Studies of these emerging infections reveal the evolutionary properties of pathogenic microorganisms and the dynamic relationships between microorganisms, their hosts and the environment. Emerging infections (EIs) can be defined as "infections that have newly appeared in a population or have existed previously but are rapidly increasing in incidence or geographic range". EIs have shaped the course of human history and have caused incalculable misery and death. In 1981, a new disease ― acquired immune deficiency syndrome (AIDS) ― was first recognized. As a global killer, AIDS now threatens to surpass the Black Death of the fourteenth century and the 1918-1920 influenza pandemic, each of which killed at least 50 million people. Of the 'newly emerging' and 're-emerging/resurging' diseases that have followed the appearance of AIDS (Fig. 1), some have been minor curiosities, such as the 2003 cases of monkeypox imported into the United States, whereas others, such as severe acute respiratory syndrome (SARS), which emerged in the same year, have had a worldwide impact. The 2001 anthrax bioterror-ist attack in the United States falls into a third category: 'deliberately emerging' diseases. EIs can be expected to remain a considerable challenge for the foreseeable future. Here we examine the nature and scope of emerging and re-emerging microbial threats, and consider methods for their control. We emphasize that emergence results from dynamic interactions between rapidly evolving infectious agents and changes in the environment and in host behaviour that provide such agents with favourable new ecological niches.