Histoplasmosis in South Carolina: support for the microfocus concept.

An outbreak of anthropurgic histoplasmosis occurred in rural South Carolina when a canebrake which served as a blackbird roost was cleared with a bulldozer. Seven days later the index patient became ill with histoplasmosis. Nine other patients contracted the disease, but only the index case was fatal. Serologic studies on the 10 patients demonstrated high titers in the histoplasmin latex agglutination test within two to three weeks after exposure. Serologic titers to the yeast-form Histoplasma capsulatum antigen in the complement fixation test appeared most frequently, but these antibodies were not diagnostic because complement-fixing antibodies to Blastomyces dermatitidis appeared at the same time. Soil studies demonstrated that viable particles of H. capsulatum persisted at declining levels over a nine-year period. A skin test survey showed that 27.3% of eighth grade students who resided within a 20 km radius of the contaminated site and who were lifelong residents of the same dwelling had a positive histoplasmin skin test.