Understanding Histoplasmosis

by National Institute of Health

What is histoplasmosis?

Histoplasmosis is a disease caused by the fungus Histoplasma capsulatum. Its symptoms vary greatly, but the disease primarily affect the lungs. Occasionally, other organs are affected. This form of the disease is called disseminated histoplasmosis, and it can be fatal if untreated.

Can anyone get histoplasmosis?

Yes. Positive histoplasmin skin tests occur in as many as 80% of the people living in areas where H. capsulatum is common, such as the eastern and central United States. Infants, young children, and older persons, in particular those with chronic lung disease are at increased risk for severe disease. Disseminated disease is more frequently seen in people with cancer or AIDS.

How is someone infected with H. capsulatum?

H. capsulatum grows in soil and material contaminated with bat or bird droppings. Spores become airborne when contaminated soil is disturbed. Breathing the spores causes infection. The disease is not transmitted from an infected person to someone else.

What are the symptoms of histoplasmosis?

Most infected persons have no apparent ill effects. The acute respiratory disease is characterized by respiratory symptoms, a general ill feeling, fever, chest pains, and a dry or nonproductive cough. Distinct patterns may be seen on a chest x-ray. Chronic lung disease resembles tuberculosis and can worsen over months or years. The disseminated form is fatal unless treated.

When do symptoms start?

If symptoms occur, they will start within 3 to 17 days after exposure; the average is 10 days.

Is histoplasmosis treatable?

Yes. Antifungal medications are used to treat severe cases of acute histoplasmosis and all cases of chronic and disseminated disease. Mild disease usually resolves without treatment. Past infection results in partial protection against ill effects if reinfected.

Where is H. capsulatum found?

H. capsulatum is found throughout the world and is endemic in certain areas of the United States. The fungus has been found in poultry house litter, caves, areas harboring bats, and in bird roosts.

About the Author

NIH is the nation's medical research agency - making important medical discoveries that improve health and save lives. The National Institutes of Health (NIH), a part of the U.S. Department of Health and Human Services, is the primary Federal agency for conducting and supporting medical research.