Histoplasmosis is an infection that is spread by the spores of the mold, Histoplasma capsulatum. Once the spore has infected a person, it turns into a yeast form which causes disease in humans. There are five forms of the disease that are recognized. Each form of the disease is characterized by unique signs and symptoms. However, generally H. capsulatum is recognized as causing a lung infection similar to other common respiratory infections.


Most people infected with H. capsulatum have no recognized illness. However, histoplasmosis is generally considered a lung infection that has five recognized forms. Each form has its own unique signs and symptoms. Symptoms normally appear within 3 to 17 days after infection and include:

Asymptomatic Form. No signs and symptoms are seen, but laboratory results are positive for infection.

Acute Benign Respiratory Form. Flu-like symptoms that include:

  • General tiredness
  • Fever
  • Chills
  • Headache
  • Muscle aches
  • Chest pains
  • Non-productive cough

Acute Disseminated Form. A form of infection that affects the entire body and may lead to death if left untreated. Symptoms include:

  • Fever
  • Vomiting
  • Diarrhea
  • Enlarged lymph nodes
  • Enlarged spleen

Chronic Disseminated Form. A form of infection that affects the entire body and may lead to death if left untreated. This form of infection usually develops over 10 to 11 months and includes the following symptoms:

  • Fever that may come and go
  • Weight loss
  • Weakness
  • Enlarged liver and spleen
  • Blood abnormalities

Chronic Pulmonary Form. This form of the disease resembles tuberculosis of the lungs. Symptoms include:

  • Night sweats
  • Loss of weight
  • Loss of appetite
  • Cough lasting longer than three weeks


Histoplasma capsulatum is a fungus found in the soil. It is especially abundant in soil contaminated with bird and bat feces. In the United States, the fungus is most commonly found in the Ohio, Missouri, and Mississippi River valleys. H. capsulatum produces spores which, when breathed in by a human, cause the disease histoplasmosis as described above.

Risk Factors

Infection by H. capsulatum can occur in anyone. People who are likely to inhale large amounts of spores found in dirt are more likely to develop signs and symptoms. These people include:

  • Farmers
  • Pest control workers
  • Construction workers
  • Roofers
  • Landscapers and gardeners
  • Anyone who has close contact with birds, including chickens, bats, or bat caves
  • Archeologists
  • Geologists

People with weakened or inhibited immune systems are at greater risk for getting severe disease. These people include:

  • People with HIV/AIDS
  • The elderly (> 65 years old)
  • Infants or young children
  • People with organ transplants
  • People on chemotherapy


Histoplasmosis is a relatively rare disease. Risk of exposure can be minimized by taking the following precautions:

  • Spray soil with water or oil to reduce dust before working
  • Anyone cleaning up sites that could be contaminated should wear masks or respirators
  • Decontamination of suspected sites with 5 percent formaldehyde solutions can be performed if deemed necessary


H. capsulatum is sensitive to many antifungals. Treatment is long-term and may require several months to a year.

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