To the Editor.—Two very interesting articles by Dunlap and Harvey appeared in the September 1967 issue of the American Journal of Diseases of Children (114: 229-252) on the carrier state and types of specific immunity in streptococcal diseases and clinical dilemma in the use of penicillin in streptococcal illness. We find the epidemiology of the subjects covered quite interesting. The first study seems to confirm what we have long suspected to be the explanation of certain facts: Any infecting organism has high initial morbidity and mortality in a previously unexposed population. After the initial epidemic, the population as a whole seems to develop a relative mass immunity, and morbidity and mortality decline. The survivors of the initial epidemic are more or less resistant, and therefore, more or less protected, against sequelae such as rheumatic fever and glomerulonephritis.
It is interesting to speculate on why the previously unexposed infected child