Nationwide Histoplasmin Sensitivity and Histoplasmal Infection

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Abstract
Histoplasmin skin tests were given to a study group of 306,000 male Navy recruits as they entered the Navy''s 2 training centers during 1958-61. The study was limited to recruits 17-21 years old who had specified their race as "white". Results are presented separately for 212,000 lifetime residents of a single State and 94,000 who had lived in more than one State. Frequency of reactions of 4 mm or more varies among States from 71.5% for lifetime residents of Kentucky to 0.7% for Rhode Island residents. Such data indicate prevalence of sensitivity to histoplasmin but not necessarily of infection with the fungus Histoplasma capsulatum, since cross-reactions to histoplasmin occur in some regions as the result of infections with agents other than Histoplasma. Frequency distributions of the sizes of reactions to histoplasmin in different parts of the country illustrate how, in some regions, the distributions of "not negative" or "significant" reactions, regardless of their frequency in the total group, approximate normal curves with similar means and standard deviations. They also show how, in other regions, normal curves with the same parameters can be fitted to only part of the observed distributions, leaving a relative excess of small reactions which are believed to represent cross- sensitization caused by infection with agents other than Histoplasma. While infection with Coccidioides may account for many of the cross-reactions in the south-west, unknown agents appear to be responsible in other parts of the country.