Histoplasmosis is a fungal disease that is spread to people by breathing in dust from pigeon or bat droppings. Fungal spores are found in the environment, especially in areas with bird and bat droppings. Birds do not get sick from exposure to histoplasmosis.
Very few people become infected with histoplasmosis. People who do become sick tend to develop pneumonia-like symptoms (fever, chest pains, and a dry or nonproductive cough) within 1–3 weeks after exposure. Infants, older people, and those with weakened immune systems are more susceptible to the fungus and might develop more serious illness.
People with weak immune systems should avoid activities such as disturbing material where there are bird or bat droppings, cleaning chicken coops, exploring caves, and cleaning, remodeling, or tearing down old buildings.
Most people who are exposed to the fungus Histoplasma never have symptoms. Other people may have flu-like symptoms that usually go away on their own.
Symptoms of histoplasmosis include:
- Fatigue (extreme tiredness)
- Chest pain
- Body aches
How soon do the symptoms of histoplasmosis appear?
Symptoms of histoplasmosis may appear between 3 and 17 days after a person breathes in the fungal spores.
How long do the symptoms of histoplasmosis last?
For most people, the symptoms of histoplasmosis will go away within a few weeks to a month. However, some people have symptoms that last longer than this, especially if the infection becomes severe.
In some people, usually those who have weakened immune systems, histoplasmosis can develop into a long-term lung infection, or it can spread from the lungs to other parts of the body, such as the central nervous system (the brain and spinal cord).
Where does Histoplasma live?
Histoplasma, the fungus that causes histoplasmosis, lives throughout the world, but it’s most common in North America and Central America. In the United States, Histoplasma mainly lives in soil in the central and eastern states, particularly areas around the Ohio and Mississippi River Valleys, but it can likely live in other parts of the U.S. as well. The fungus also lives in parts of Central and South America, Africa, Asia, and Australia.
Histoplasma grows best in soil that contains bird or bat droppings. Bats can get histoplasmosis and spread the fungus in their droppings.
This map shows the approximate areas (called “endemic areas”) where Histoplasma is known to live or is suspected to live in the U.S. Much of what’s known about where the fungus lives in the U.S. is based on studies performed in the late 1940s and early 1950s.
Life cycle of Histoplasma
Histoplasma spores circulate in the air after contaminated soil is disturbed. The spores are too small to see without a microscope. When people breathe in the spores, they are at risk for developing histoplasmosis. After the spores enter the lungs, the person’s body temperature allows the spores to transform into yeast. The yeast can then travel to lymph nodes and can spread to other parts of the body through the bloodstream.
I’m worried that Histoplasma is in the soil or in bird/bat droppings near my home. Can someone test the environment to find out if the fungus is there?
No, in this situation, testing the environment for Histoplasma isn’t likely to be useful because the fungus is thought to be common in the environment in certain areas. A soil sample that tests positive for Histoplasma doesn’t necessarily mean that it’s a source of infection, and a sample that tests negative doesn’t necessarily mean that the fungus isn’t there. Also, there are no commercially-available tests to detect Histoplasma in the environment. Testing environmental samples for Histoplasma is currently only done for scientific research. If there are bird or bat droppings near your home, you should have it cleaned up, if possible. If it’s not possible to clean up, try not to disturb it.
Who gets histoplasmosis?
Anyone can get histoplasmosis if they’ve been in an area where Histoplasma lives in the environment. Histoplasmosis is often associated with activities that disturb soil, particularly soil that contains bird or bat droppings. Certain groups of people are at higher risk for developing the severe forms of histoplasmosis:
- People who have weakened immune systems, for example, people who:
- Have HIV/AIDS
- Have had an organ transplant
- Are taking medications such as corticosteroids or TNF-inhibitors)
- Adults aged 55 and older