Outbreak of histoplasmosis among cavers attending the National Speleological Society Annual Convention, Texas, 1994

In June 1994, Is people developed serologically confirmed histoplasmosis fo llowing cave exploration associated with the annual National Speleological Society Convention in Bracketville, Texas. Six others had an undiagnosed il lness suspected to be histoplasmosis. Two persons were hospitalized. We con ducted a survey of convention attendees and a nested case-control study of those entering caves. We also conducted a histoplasmin skin test survey of a subgroup of the society, the Texas Cavers Association, who were attending a reunion in October 1994. Among the national convention attendees, exposu re to two caves was identified as responsible for 22 (92%) of the 24 cases; 12 (75%) of 16 people exploring one cave (Cave A) and 10 (77%) of 13 explo ring a separate cave (Cave B) developed acute histoplasmosis. Additional ri sk-factors included fewer years of caving experience, longer time spent in the caves, and entering a confined crawl space in Cave A. Of 113 participan ts in the separate skin test survey, 68 (60%) were found to be skin test po sitive, indicating previous exposure to Histoplasma capsulatum. A positive skin test was significantly associated with male sex and more years of cavi ng experience. Those less experienced in caving associations should be taug ht about histoplasmosis, and health care providers should pursue histories of cave exposure for patients with bronchitis or pneumonia that does not re spond to initial antibiotic therapy.