Severity of illness depends on host immunity and the intensity of the exposure. Symptomatic infections (1%) usually present 3 to 17 days after exposure as an influenza-like illness. Acute pulmonary histoplasmosis is often self-limiting; symptoms include fever, malaise, cough, headache, chest pain, chills, and myalgias. Persons with a history of pulmonary disease can develop chronic pulmonary histoplasmosis. Immunosuppressed persons are at risk for developing disseminated histoplasmosis.
Histoplasma capsulatum var. capsulatum (near-worldwide distribution) and Histoplasma capsulatum var. duboisii (in Africa).1
Reservoir and endemic areas
Soil, particularly when heavily contaminated with bird or bat droppings. Endemic areas include the central and eastern United States, particularly areas around the Ohio and Mississippi River Valleys,2 as well as parts of Central and South America,3 Africa,4 Asia,5 and Australia.6
Histoplasmosis is typically acquired via inhalation of airborne microconidia, often after disturbance of contaminated material (e.g., activities such as spelunking, cleaning chicken coops, or construction). Primary cutaneous histoplasmosis and solid organ donor-derived histoplasmosis are extremely uncommon.7,8
Can include pericarditis, broncholithiasis, pulmonary nodules, mediastinal granuloma, or mediastinal fibrosis.1,9 In persons who develop progressive, chronic, or disseminated disease, symptoms may persist for months or longer. Mortality is high in HIV-infected persons who develop disseminated histoplasmosis.
Histoplasma antigen detection in urine and/or serum is the most widely used and most sensitive method for diagnosing acute histoplasmosis.1 Other methods include antibody tests, culture, and microscopy.1
- Antigen detection: Enzyme immunoassay (EIA) is typically performed on urine and/or serum, but can also be used on cerebrospinal fluid or bronchoalveolar lavage fluid. Sensitivity is generally higher in urine than in serum, particularly for HIV-infected persons with disseminated histoplasmosis.
- Antibody tests: Because development of antibodies to Histoplasma can take two to six weeks, antibody tests are not as useful as antigen detection tests in diagnosing acute histoplasmosis or in immunosuppressed persons, who may not mount a strong immune response.
- Immunodiffusion (ID): Tests for the presence of H (indicates chronic or severe acute infection) and M (develops within weeks of acute infection and can persist for months to years after the infection has resolved) precipitin bands; ~80% sensitivity.
- Complement Fixation (CF): Complement-fixing antibodies may take up to 6 weeks to appear after infection. CF is more sensitive but less specific than immunodiffusion.
- Culture: can be performed on tissue and body fluids, but may take up to 6 weeks to become positive; most useful in the diagnosis of the severe forms of histoplasmosis.
- Microscopy: for detection of budding yeast in tissue or respiratory secretions; low sensitivity.
- Polymerase Chain Reaction (PCR): PCR for detection of Histoplasma directly from clinical specimens is still experimental, but promising.
People in endemic areas, particularly those who have occupations or participate in activities exposing them to soil that contains bird or bat droppings. Disseminated histoplasmosis is more likely to occur in immunosuppressed persons (HIV/AIDS,10-11 organ transplant,11-12 or use of immunosuppressive medications11,13), infants,14 or adults age 55 years and older.15
Surveillance and statistics
Histoplasmosis is reportable in the following states and U.S. territories: Alabama, Arkansas, Delaware, Illinois, Indiana, Kentucky, Michigan, Minnesota, Mississippi, Nebraska, Pennsylvania, Puerto Rico, Rhode Island, and Wisconsin. Check with your local, state, or territorial public health department for more information about disease reporting requirements and procedures in your area. Click here for histoplasmosis statistics.
Areas for further research
- Developing and validating improved diagnostic tests
- Developing improved methods for detection of Histoplasma in environmental samples
- Identifying safe and effective environmental remediation measures
- Determining trends in histoplasmosis incidence and the global burden of infection