The epidemiology and natural history of streptococcal pyoderma: an endemic disease of the rural southern United States.

In order to study the natural history of endemic pyoderma, the host and environmental risk factors to infection, the immunologic response and the risk of acute glomerulonephritis (AGN) a prospective study was done between June 29 and December 13, 1970 in 444 black children aged 2-6 years attending project Headstart centers in Holmes County, Mississippi. The weekly prevalence of pyoderma was about 40-50% during July and August but decreased to 4% during the last week of the study. "Pyoderma-type" serotypes of group A streptococci were isolated from about 70% of the skin lesions and similar serotypes were also commonly isolated from the pharynx. The seasonal prevalence and T and M typing pattern of most of the pharyngeal isolates mirrored the skin isolates. Many of the streptococci appear to belong to previously unrecognized M-types and one strain has been designated provisional M type 67 by the International Subcommittee on Pneumococci and Streptococci. Staphylococci were also isolated commonly from the skin lesions, especially late in their evolution. Despite an 80% incidence of streptococcal pyoderma during the summer months, only 3 children (0.67%) developed AGN; all of these children had clinically mild disease. The risk of a major outbreak of AGN in populations like these is substantial. Surveillance for clusters of AGN is indicated and widespread benzathine penicillin prophylaxis should be used in the event of an outbreak. Also, further research to determine the long term prognosis of clinically mild AGN and to detect useful laboratory markers of nephritogenicity are indicated.