This infection is caused by a fungus present in soil contaminated with bat or bird droppings, particularly in eastern and central United States as well as in Mexico. It gets into the air when the soil is disturbed, such as when people explore caves. It is not passed from person to person.

Symptoms can include:

• fever
• weight loss
• cough
• shortness of breath
• abdominal pain

Histoplasmosis can be quite serious but is treatable with medications, which need to be continued until the immune system has improved with HIV treatment. In some parts of the country, medication is given to patients with HIV who have low CD4 counts in order to prevent histoplasmosis.