From the Guidelines
Pulmonary histoplasmosis risk factors primarily include activities or environments that expose individuals to Histoplasma capsulatum spores, with the most significant risk factor being living in or visiting endemic regions, particularly the Ohio and Mississippi River valleys in the United States, as noted in the 2007 update by the Infectious Diseases Society of America 1. The most important risk factors for pulmonary histoplasmosis include:
- Living in or visiting endemic regions, such as the Ohio and Mississippi River valleys in the United States, parts of Central and South America, Africa, and Asia
- Occupational exposures, including farming, construction work, spelunking, and archaeology, which increase the risk of exposure to H. capsulatum spores due to soil disturbance activities
- Specific environmental exposures, such as working with bird or bat droppings, cleaning chicken coops, demolishing old buildings, or disturbing soil in areas with high concentrations of bird or bat excrement
- Immunocompromised individuals, including those with HIV/AIDS, organ transplant recipients, and patients on immunosuppressive medications like TNF inhibitors or corticosteroids, who face a significantly higher risk of developing severe or disseminated disease, as highlighted in the guidelines for prevention and treatment of opportunistic infections in HIV-infected adults and adolescents 1
- Other risk factors, including advanced age, underlying lung diseases such as COPD or emphysema, and diabetes mellitus, which can increase the risk of developing severe or disseminated disease The risk of pulmonary histoplasmosis increases with the concentration of spores inhaled, which explains why outbreaks often occur when groups disturb heavily contaminated areas, releasing large numbers of spores into the air that can be inhaled deep into the lungs, as discussed in the clinical practice guidelines for the management of patients with histoplasmosis 1.
From the Research
Risk Factors for Pulmonary Histoplasmosis
The risk factors for pulmonary histoplasmosis include:
- Immunocompromised status, as individuals with weakened immune systems are more susceptible to severe and disseminated forms of the disease 2, 3, 4
- Occupational exposure to soil containing bird or bat droppings, particularly in areas where Histoplasma is endemic 5
- Inhaling a large burden of organisms from the environment, which can lead to severe pneumonia 6
- Severe chronic obstructive pulmonary disease, as chronic histoplasmosis occurs almost exclusively in these patients 6
- Living in areas of high endemicity, such as the Mississippi and Ohio River Valleys of North America and parts of Central and South America 2
High-Risk Populations
Certain populations are at higher risk of developing pulmonary histoplasmosis, including:
- Immunocompromised individuals, such as those with HIV/AIDS or undergoing chemotherapy 2, 3, 4
- Workers in occupations that involve exposure to soil containing bird or bat droppings, such as construction or agricultural workers 5
- Travelers to areas where Histoplasma is endemic 4
- Individuals with severe chronic obstructive pulmonary disease 6