A common lung infection hides in soil tainted by bird and bat droppings

Countries & Cities · Published 3 October 2026 Swipe more like this →

In short: Most people who breathe in the spores of the fungus Histoplasma capsulatum never realize they have been infected. Yet, for those with weakened immune systems, this environmental hazard can trigger life-threatening complications. Understanding where this fungus thrives is the first step in protecting yourself from a frequently misdiagnosed illness.

Histoplasmosis is caused by Histoplasma capsulatum, a fungus that thrives in damp, organic-rich soil, particularly in areas contaminated by bird or bat droppings. It is notably prevalent in the Mississippi and Ohio river valleys in the United States, though it is found globally. The infection occurs when airborne spores are released during activities that disturb the soil, such as construction, demolition, or cave exploration. Once inhaled, the spores reach the lungs, where they transform into a yeast form that can be ingested by white blood cells.

For the vast majority of people, the immune system successfully contains the fungus, often walling it off with granulomas without the person ever experiencing symptoms. In fact, it is estimated that about 75% of adults living in endemic areas have been infected at some point in their lives. When symptoms do occur, they typically appear 3 to 17 days after exposure and often mimic common bacterial or viral pneumonias, leading to frequent misdiagnosis. Common signs include fever, chills, fatigue, and a dry cough.

The disease becomes dangerous when it progresses beyond a mild, self-limiting infection. Chronic histoplasmosis, which often affects individuals with underlying lung conditions like COPD, can cause long-term damage that resembles tuberculosis. More severe is progressive disseminated histoplasmosis, where the fungus spreads from the lungs to other organs, including the liver, brain, and adrenal glands. This form is particularly life-threatening for infants and those with compromised immune systems, such as patients with advanced HIV or those undergoing chemotherapy. Treatment for severe cases involves antifungal medications like itraconazole or amphotericin B, with courses lasting from three months up to a year.

General information, not professional advice. Spotted an error? Flag the card or see corrections and complaints.

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