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Histoplasmosis -- Kentucky, 1995

Histoplasmosis is an infection resulting from inhalation of spores from the dimorphic fungus Histoplasma capsulatum; the condition primarily affects the lungs. During August 1995, the Department for Health Services, Kentucky Cabinet for Human Resources (KDHS), and local public health officials investigated two unrelated outbreaks of acute histoplasmosis in eastern Kentucky. This report summarizes preliminary findings of the investigations of these outbreaks.

Outbreak 1

On June 27, 1995, a crew of five workers began partial demolition of an abandoned city hall building in a community in Kentucky. At the time of demolition, a colony of bats had been observed in the vicinity of the building, and an approximately 2-foot-deep pile of debris covered with bat guano had accumulated in the building. During the demolition, none of the workers wore personal protective equipment (PPE) (i.e., respirators, eye protection, gloves, or protective clothing). Within 3 weeks, all five workers required treatment for acute respiratory illnesses, and three had been hospitalized. Lung biopsies were obtained from the three hospitalized patients; Giemsa stained tissue from the lung biopsy of one of the patients suggested the presence of H. capsulatum.

From the demolition crew, local physicians, medical records, personnel from local hospitals and clinics, and community members, KDHS investigators gathered information about persons who possibly had been exposed to H. capsulatum during the demolition. A total of 55 persons (including the demolition crew) were identified who had worked in or near the building or lived in the area during the demolition. Each was questioned about a history of symptoms (including fever greater than or equal to 101 F {greater than or equal to 38.3 C}, chills, night sweats, cough, headache, fatigue, and myalgia) during July 1-August 3. Immunodiffusion and complement fixation tests to detect antibodies to H. capsulatum were performed by CDC on serum from these 55 persons. A case of acute Histoplasma infection was defined as a positive serologic test (the presence of M or H band on immunodiffusion or 1:32 or higher titer by complement fixation), or the presence of at least three of the clinical features during July 1-August 3 in a person working in or near or living near the building.

Overall, 19 of the 55 persons had a serologic test or clinical features that met the case definition. Of these, 12 persons had participated in the demolition: five had worked as the crew, one truck driver had hauled the debris to the dump site, four workers from the city workshop had helped the truck driver haul and dump the debris, and two had washed the building. Three persons had visited the building during the demolition, and four others had lived or worked within 500 yards of the building.

Outbreak 2

KDHS is investigating a second outbreak of histoplasmosis in a different community located 80 miles north of the first city. During March 17-April 5, 1995, the attic of a building was repaired; bird and bat guano had accumulated in the attic. Within 3 weeks after completion of the repairs, 13 employees who worked in the building required treatment for acute respiratory illnesses; of these, two had been hospitalized. On June 26, a lung biopsy was obtained from one of the two hospitalized patients; Giemsa stained tissue from the lung biopsy suggested the presence of H. capsulatum. Serologic testing was performed for 16 employees; based on preliminary findings, 11 (including 10 of those who had received treatment) had acute Histoplasma infection confirmed serologically.

Reported by: L Leslie, MD, C Arnette, MD, Archer Memorial Clinic, A Sikder, MD, Big Sandy Health Care, J Adams, MD, C Holbrook, J Bond, Floyd County Health Dept, Prestonsberg; B King, K Roberts, City Hall, Russell; MS Patrick, Greenup County Health Dept, Greenup; C Palmer, MD, R Finger, MD, State Epidemiologist, Dept for Health Svcs, Kentucky Cabinet for Human Resources. JW Tomford, MD, Cleveland Clinic Foundation, Ohio. T Rushton, MD, Marshall Univ, Huntington, West Virginia. Emerging Bacterial and Mycotic Diseases Br, Div of Bacterial and Mycotic Diseases, National Center for Infectious Diseases; Div of Field Epidemiology, Epidemiology Program Office, CDC.

Editorial Note

Editorial Note: The outbreaks of acute histoplasmosis in Kentucky most likely were caused by inhalation of spores of H. capsulatum dispersed from contaminated bird and bat guano. H. capsulatum grows well in soil enriched with bird or bat guano (1), and histoplasmosis is endemic in states in the Mississippi and Ohio river valleys, including Kentucky, Illinois, Indiana, Missouri, Ohio, and Tennessee (2). In southern Kentucky, middle Tennessee, and surrounding areas, histoplasmin skin testing has been positive in up to 95% of the population (3). Although partial immunity to histoplasmosis can occur following infection with H. capsulatum, susceptibility to the infection remains, especially when the level of exposure to spores is high. The outbreaks in Kentucky are consistent with previous outbreaks of acute histoplasmosis that have been associated with disturbance of bird and bat guano during cleaning, construction, and recreational (e.g., cave exploration) activities (1,4,5).

The clinical spectrum of infection with H. capsulatum includes asymptomatic infection (most cases); mild, self-limited influenza-like illness; acute or chronic pulmonary infection; and disseminated disease. Disseminated disease is more likely to occur in the very young, the elderly, and immunocompromised persons (e.g., persons being treated for cancer with chemotherapy or persons with human immunodeficiency virus infection) and can be life-threatening. The incubation period ranges from 5 to 18 days. Acute histoplasmosis usually can be diagnosed by serologic tests (immunodiffusion and complement fixation) and sometimes by positive sputum culture or lung biopsy culture. Chest radiography can be useful in diagnosing histoplasmosis when interstitial infiltrates and/or hilar adenopathy are present; however, histoplasmosis can be difficult to distinguish from other pulmonary mycoses and from mycobacterial infections of the lung.

When any material contaminated with bird or bat guano is to be disturbed in an area with endemic histoplasmosis, precautions should be taken to control dust aerosolization and to protect workers and persons in surrounding areas from exposure through inhalation (6). Water should be sprayed at low velocity on contaminated material to reduce the likelihood of aerosolization. During the removal of potentially contaminated material, PPE is necessary to protect workers from exposure to H. capsulatum (6); however, the type and level of PPE will vary based on the risk for exposure. Material that is to be removed and disposable PPE used during removal should be collected and sealed in heavy-duty plastic bags and disposed of in a landfill. Formaldehyde solution (3%-5%) has been reported to be effective in disinfecting soil contaminated with H. capsulatum (7); however, exposure to formaldehyde should be controlled to the lowest feasible limit (8). Additional information about prevention and control of histoplasmosis can be obtained from CDC's Division of Bacterial and Mycotic Diseases, National Center for Infectious Diseases, Mailstop A-13, 1600 Clifton Rd., N.E., Atlanta, GA 30333; telephone (404) 639-3158.


  1. DiSalvo AF, Johnson WM. Histoplasmosis in South Carolina: support for the microfocus concept. Am J Epidemiol 1979;109:480-92.

  2. Rippon JW. Medical mycology: the pathogenic fungi and the pathogenic actinomycetes. 3rd ed. Philadelphia, Pennsylvania: W.B. Saunders Company, 1988.

  3. Schulman ST, Phair JP, Sommers HM. The biologic and clinical basis of infectious diseases. 4th ed. Philadelphia, Pennsylvania: W.B. Saunders Company, 1992.

  4. Kaufman L. Laboratory methods for the diagnosis and confirmation of systemic mycoses. Clin Infect Dis 1992;14(suppl 1):S23-S29. 5. Schlech WF, Wheat LJ, Ho JL, et al. Recurrent urban histoplasmosis -- Indianapolis, Indiana, 1980-81. Am J Epidemiol 1983;118:301-12.

  5. Lenhart SW. Case studies: recommendations for protecting workers from Histoplasma capsulatum exposure during bat guano removal from a church's attic. Applied Occupational and Environmental Hygiene 1994;9:230-6.

  6. Tosh FE, Weeks RJ, Peiffer FR, Hendrichs SL, Greer DL, Chin TD. The use of formalin to kill Histoplasma capsulatum at an endemic site. Am J Epidemiol 1967;85:259-65.

  7. NIOSH/Occupational Safety and Health Administration. Current intelligence bulletin no. 34: formaldehyde -- evidence of carcinogenicity. Cincinnati, Ohio: US Department of Health and Human Services, Public Health Service, CDC, 1980; DHHS publication no. (NIOSH)81-111.

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