Since Pasteur's discovery of streptococci in the blood of a patient dying of sepsis approximately a century ago, the diseases with which the germ has been associated have undergone striking secular variation.1 In fact, the history of the classification of streptococci is still evolving, because like other infectious diseases, not only do human historical, social, and economic factors cause variations in the frequency, severity, and manifestations of infections due to group A streptococci, but these versatile microorganisms change rapidly—presumably by chromosomal and extrachromosomal DNA alterations, enzyme induction, and by many selective pressures in the environment.
See also p 1421.
The history of scarlet fever,2 for example, reminds us that the epidemiology of this clinical syndrome led early students of the disease to resist the notion that a single species could cause the variable syndromes of scarlatina.3 These included the scarlatinal "Nachkrankheiten" of Bela Schick,4 namely, glomerulonephritis