Evolving microbes and re-emerging streptococcal disease

Changes in demography, lifestyle, and agriculture are all cited as causes of emerging and re-emerging infectious diseases. Yet microbes play an active role in these events. They are constantly evolving. This article reviews the general principles of bacterial genetics that influence emergence or re-emergence of infectious diseases and discusses re-emerging streptococcal infections, which are a major public health concern today. The scarlet fever pandemic of the 19th century serves as a case study of the waxing and waning of epidemics as biological expressions of host-microbe associations. This article discusses the possible relationship between this earlier pandemic and the emergence of streptococcal toxic shock syndrome and the re-emergence of rheumatic fever, notably in the Salt Lake City area. A general strategy for confronting emerging infectious diseases is applicable to this re-emergence of streptococcal diseases.