Evolving microbes and re-emerging streptococcal disease.

Microbes will evolve and the epidemics they cause will continue to occur in the future as they have in the past. Microbes emerge from the evolutionary stream as a result of genetic events and selective pressures that favor new over old. It is nature's way. Microbes and vectors swim in the evolutionary stream, and they swim much faster than humans. Bacteria reproduce every 30 minutes and, for them, a millennium is compressed into a fortnight. They are "fleet afoot," and the pace of research must keep up with them or they will overtake. Microbes were here on Earth 2 billion years before humans arrived, learning every trick of the trade for survival, and they are likely to be here 2 billion years after we depart. Current research on the rise and decline of epidemics is broadly based and includes evolutionary and population genetics of host-microbe relationships. Within this context, the 19th century pandemic of scarlet fever has been described. The possibility is raised that the GAS, which currently cause STSS, possess some of the virulence factors that caused pandemic scarlet fever. Furthermore, the GAS isolated during the recent outbreaks of ARF in certain locales in the United States have the virulence properties of the GAS frequently isolated in the first half of the 20th century. Finally, it is suggested that the strategy to confront emerging infectious diseases should be the study of infectious diseases from all points of view. They remain the greatest threats to our society.