Dynamics of emergence.

I have touched briefly here on the complex matrix of social, economic, political, and ecologic factors that have played a major role in the emergence of microbial diseases. But beyond these factors that contribute to the emergence of new infectious diseases, we must also recognize changes in microbial agents, human populations, insect vectors, and the ecologic relationships among them. Microbes and vectors swim in the evolutionary stream and they swim much faster than we do. Bacteria reproduce every 30 min; for them a millennium is compressed into a fortnight. Microbes were here, learning every trick for survival, 2 billion years before humans arrived, and it is likely that they will be here 2 billion years after we depart. Furthermore, science cannot halt the future occurrence of new microbes, which emerge from the evolutionary stream as a consequence of genetic events and selective pressures that favor the new over the old. It is nature's way. For all of these reasons, old and new infections will occur in the future as they have in the past. Surveillance efforts, both in the United States and other regions of the world, will be needed to blunt the emergence of such infections and to forestall epidemics and pandemics. But surveillance alone cannot detect the unexpected emergence of future microbes or prepare the defense against them. That will require a broadly based research effort to devise new methods of diagnosis, treatment, and prevention. We must swim with the microbes and study their survival and adaptation to new habitats.(ABSTRACT TRUNCATED AT 250 WORDS)