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. 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. 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.
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. If symptoms occur, they will start within 3
to 17 days after exposure; the average is 10 days.
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.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.
It is not practical to test or decontaminate most sites that may be contaminated with H. capsulatum, but the following precaution can be taken to reduce a person's risk of exposure: