A streptococcal epidemic in an isolated civilian population with institution of mass prophylaxis

A virulent streptococcal epidemic involving two strains concurrently occurred in Eagle Butte, South Dakota, in the spring of 1965. Index cases of acute rheumatic fever and acute glomerulonephritis occurred in this isolated civilian population. Certain criteria, previously proposed, confirm streptococcal epidemicity and offer guidelines in the consideration of mass prophylaxis. A mass prophylaxis regimen was applied to this population. The epidemic was interrupted and additional cases of nonsuppurative sequelae may have been prevented.