Contrasting Epidemiology of Acute Rheumatic Fever and Acute Glomerulonephritis

Abstract

Studies of streptococcal infection in the mid-South, where acute rheumatic fever and pyoderma nephritis occur in the same population, suggest quantitative and qualitative factors tending to reduce the frequency of acute rheumatic fever. Quantitatively, beta-hemolytic streptococci isolated from ambulatory patients with pharyngitis at City of Memphis Hospitals were characterized by relatively low percentages of Group A and M-typable strains and weak immune responses. Qualitatively, throat strains fell into the M and T serotypes generally associated with skin infections rather than with pharyngitis. In addition, there was a temporal disparity between the occurrence of acute rheumatic fever and acute glomerulonephritis in patients admitted to these hospitals. Despite the frequent isolation of "skin strains" from the throat, rheumatic fever did not appear during the peak of the pyoderma season. These findings support the concept that "pyoderma strains" of streptococci are associated with little or no rheumatic fever.