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Learn About Histoplasmosis

Key Facts

  • Histoplasmosis is the most common of the three major endemic (limited to specific geographical areas) fungal infections of North America.
  • Histoplasmosis is usually acquired by breathing fungal spores from the soil or in construction projects.  It is not contagious.
  • In otherwise healthy persons, histoplasmosisis usually mild and resolves on its own.
  • Persons with weakened immune systems are more likely to develop severe forms of histoplasmsosis that can be life-threatening.
  • Some patients, particularly smokers and patients who suffer from chronic obstructive pulmonary disease (COPD) can develop a chronic and progressive form of histoplasmosis that requires a long treatment.

What Is Histoplasmosis?

Histoplasmosis is an infection caused by the fungus Histoplasma capsulatum. Histoplasmosis is the most common of the three major endemic (limited to a specific geographical area) fungal infections of North America. (The other two are blastomycosis and coccidiodomycosis). These fungi are found in soil, and the soil and climate of specific regions are best suited for the growth of these fungi. The vast majority of histoplasmosis occurs in the states surrounding the Ohio and Mississippi river valleys covering a large area of the Midwestern United States. Histoplasmosis is also common in Latin America and Africa.

How Histoplasmosis Affects Your Body

You get histoplasmosis by inhaling infectious fungal spores. These spores are usually released into the air by activities that disturb the earth such as digging, demolishing old buildings and cutting down old trees. Most infections occur as outbreaks related to large construction projects. Others are related to recreational activities such as spelunking in bat-infested caves. Once inhaled, the spores can cause a lung infection (pneumonia) which, if not controlled by a healthy immune system, can spread throughout the body and cause what is known as "disseminated disease," the most severe and life-threatening form of histoplasmosis.

Activities and exposures linked to the acquisition of histoplasmosis

Sites likely to have Histoplasma

Activities likely to cause exposure to Histoplasma



Chicken coops

Cleaning, demolitions, and use of bird droppings in gardens

Bird roost


Prison grounds and school yards

Cleaning and routine activities

Decayed wood pile

Cutting and transporting the wood

Dead trees

Cutting wood and recreation

Old buildings

Demolition, remodeling, cleaning

How Serious Is Histoplasmosis?

The severity of histoplasmosis depends on three factors:

  • The degree of exposure to the fungus
  • How strong your immune system is
  • How healthy your lungs are

Most histoplasmosis infections have mild or no symptoms that resolve on their own; these people don't even know they were infected or thought they had "the flu" until signs of the infection show up on an X-ray taken later for another reason. The infections can be severe if the exposure is heavy or if you have a weak immune system. In these cases, histoplasmosis can cause severe and life-threatening illness.

    This content was developed in partnership with the CHEST Foundation, the philanthropic arm of the American College of Chest Physicians.

    Page Last Updated: August 1, 2019

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