Histoplasmosis is an infection caused by breathing in spores of a fungus often found in bird and bat droppings. People usually get it from breathing in these spores when they become airborne during demolition or cleanup projects.

Soil contaminated by bird or bat droppings also can spread histoplasmosis, putting farmers and landscapers at a higher risk of the disease. In the United States, histoplasmosis commonly occurs in the Mississippi and Ohio River valleys. But it can occur in other areas, too. It also occurs in Africa, Asia, Australia, and in parts of Central and South America.

Most people with histoplasmosis never develop symptoms and aren't aware they're infected. But for some people — mainly infants and those with weakened immune systems — histoplasmosis can be serious. Treatments are available for even the most severe forms of histoplasmosis.

The mildest forms of histoplasmosis cause no signs or symptoms. But severe infections can be life-threatening. When signs and symptoms occur, they usually appear 3 to 17 days after exposure and can include:

• Fever
• Chills
• Headache
• Muscle aches
• Dry cough
• Chest pain
• Tiredness

Some people with histoplasmosis also get joint pain and a rash. People who have a lung disease, such as emphysema, can develop chronic histoplasmosis.

Signs of chronic histoplasmosis can include weight loss and a bloody cough. Chronic histoplasmosis symptoms sometimes mimic those of tuberculosis.

Severe histoplasmosis

The most severe variety of histoplasmosis occurs mainly in infants and in people with weakened immune systems. Called disseminated histoplasmosis, it can affect nearly any part of your body, including your mouth, liver, central nervous system, skin and adrenal glands. If untreated, disseminated histoplasmosis is usually fatal.

Contact your health care provider if you develop flu-like symptoms after being exposed to bird or bat droppings — especially if you have a weakened immune system.

Histoplasmosis is caused by the reproductive cells (spores) of the fungus Histoplasma capsulatum. They float into the air when dirt or other material is disturbed.

The fungus thrives in damp soil that's rich in organic material, especially the droppings from birds and bats. It's particularly common in chicken and pigeon coops, old barns, caves, and parks.

Histoplasmosis isn't contagious, so it can't be spread from person to person. If you've had histoplasmosis, you can get it again. However, if you do get it again, the illness will likely be milder the second time.

The chances of developing histoplasmosis symptoms increase with the number of spores you inhale. People more likely to be exposed include:

• Farmers
• Pest control workers
• Poultry keepers
• Construction workers
• Roofers
• Landscapers and gardeners
• Cave explorers
• Demolition workers

Most at risk of severe infection

Children younger than age 2 and adults age 55 and older have weaker immune systems. Because of this, they're more likely to develop disseminated histoplasmosis — the most serious form of the disease. Other factors that can weaken your immune system include:

• HIV or AIDS
• Cancer chemotherapy
• Corticosteroid drugs, such as prednisone
• Tumor necrosis factor inhibitors, often used to control rheumatoid arthritis
• Medications that prevent rejection of organ transplants

Histoplasmosis can cause many serious complications, even in otherwise healthy people. For infants, older adults and people with weakened immune systems, the potential problems are often life-threatening.

Complications can include:

• Acute respiratory distress syndrome. Histoplasmosis can damage lungs to the point that the air sacs begin filling with fluid. This prevents good air exchange and can deplete the oxygen in your blood.
• Heart problems. Inflammation of the sac that surrounds your heart (pericardium) is called pericarditis. When the fluid in this sac increases, it can interfere with the heart's ability to pump blood.
• Adrenal insufficiency. Histoplasmosis can harm your adrenal glands, which produce hormones that give instructions to virtually every organ and tissue in your body.
• Meningitis. In some cases, histoplasmosis can cause this inflammation of the membranes surrounding your brain and spinal cord.

It's difficult to prevent exposure to the fungus that causes histoplasmosis, especially in areas where the disease is widespread. But taking the following steps might help reduce the risk of infection:

• Avoid exposure. Avoid projects and activities that might expose you to the fungus, such as cave exploring and raising birds, such as pigeons or chickens.
• Spray contaminated surfaces. Before you dig soil or work in an area that could harbor the fungus that causes histoplasmosis, soak it with water. This can help prevent spores from being released into the air. Spraying chicken coops and barns before cleaning them also can reduce your risk.
• Wear a respirator mask. Consult the National Institute for Occupational Safety and Health to determine which type of mask will provide protection for your level of exposure.

Diagnosing histoplasmosis can be complicated, depending on what parts of your body are affected. While testing might not be necessary for mild cases of histoplasmosis, it can be crucial in treating life-threatening cases.

Your doctor may suggest searching for evidence of the disease in samples of:

• Lung secretions
• Blood or urine
• Lung tissue (biopsy)
• Bone marrow

Treatment usually isn't necessary if you have a mild case of histoplasmosis. But if your symptoms are severe or if you have the chronic or disseminated form of the disease, you'll likely need treatment with one or more antifungal drugs. If you have a severe form of the disease, you might need to continue to take medications for three months to a year.

You're likely to start by seeing your primary care provider, who might refer you to a specialist in infectious diseases. Depending on your symptoms and the severity of your infection, you might also see other doctors, such as a lung specialist (pulmonologist) or a heart specialist (cardiologist).

What you can do

Make a list of:

• Your symptoms, including any that seem unrelated to the reason for which you scheduled the appointment, and when they began
• Key personal information, including possible exposure to areas with numerous birds or bats
• All medications, vitamins or other supplements you take, including doses
• Questions to ask your doctor

For histoplasmosis, questions to ask your health care provider include:

• What's the most likely cause of my symptoms?
• How could I have gotten this infection?
• What tests do I need?
• Will I need treatment and, if so, which do you recommend?
• What side effects can I expect from treatment?
• I have other health conditions. How can I best manage these conditions together?
• Are there printed materials I can have? What websites do you recommend?

What to expect from your health care provider

Your health care provider is likely to ask you questions, including:

• Have your symptoms been continuous or occasional?
• How severe are your symptoms?
• Do you work outdoors?
• Have you spent time in areas with there are a lot of birds?
• Have you spent time in caves or other areas where bats might live?