Histoplasmosis

What is histoplasmosis?

Histoplasmosis is a fungal infection that mostly affects the lungs and is caused by the Histoplasma fungus. It is found in many parts of the United States, particularly in areas with soil that contains bird or bat droppings. Because symptoms can be similar to common respiratory illnesses, histoplasmosis is often not diagnosed right away. The fungus grows in soil, especially in places like caves, old buildings, chicken coops, and areas where birds or bats have lived. People become infected by breathing in tiny (microscopic) fungal spores released into the air when soil that contains the fungus is disturbed. Histoplasmosis does not spread from person to person.

What are the symptoms of histoplasmosis?

Most people exposed to Histoplasma have no symptoms at all. When symptoms of histoplasmosis do occur, they typically appear 3 to 17 days after exposure and may include:

  • Fever and chills
  • Dry cough
  • Chest discomfort
  • Fatigue
  • Headache
  • Muscle aches

How is histoplasmosis diagnosed?

Doctors may consider histoplasmosis in people who have symptoms of lung infection that do not improve with standard treatments, particularly if they have been exposed to environments where the fungus is known to live.

Diagnosis often involves a combination of clinical evaluation and laboratory testing, such as:

  • Chest X-rays or CT scans
  • Urine or blood antigen tests
  • Antibody tests
  • Microscopic examination or culture of respiratory samples, tissue, or body fluids

How serious is histoplasmosis?

Most cases of histoplasmosis are mild. However, the infection can become serious in certain situations:

  • In people with weakened immune systems
  • In infants and older adults
  • When a large number of spores are inhaled

Severe forms of the disease can require hospitalization and antifungal treatment. In people with weakened immune systems, the infection can move beyond the lungs and affect other organs including the liver, spleen, and bone marrow. This form, called disseminated histoplasmosis, is rare but life-threatening if not treated promptly.

Who is at higher risk of becoming infected with Histoplasma?

People at higher risk include those who are exposed to environments where bird or bat droppings are present, especially when these areas are disturbed. This includes:

  • Construction and demolition workers
  • Farmers and landscapers
  • Cave explorers (spelunkers)
  • People cleaning chicken coops, barns, or attics

How can I lower my risk of getting histoplasmosis?

To reduce risk:

  • Avoid disturbing soil or materials that may contain bird or bat droppings
  • Use protective equipment (like masks or respirators) when working in high-risk environments
  • Follow workplace safety guidelines if your job involves exposure to dust or contaminated areas

For more information, see Histoplasmosis guidance for workers (PDF) (cdc.gov)

If you have a weakened immune system, talk with your health care provider before spending time in areas where exposure is more likely.

How is histoplasmosis treated?

Mild cases often do not require treatment and may resolve on their own. For moderate to severe cases, prescription antifungal medications are used. The choice of medication and how long they are needed depends on the severity of the illness and the person's overall health. In more serious cases, treatment may last several months or longer.

Can pets become infected with Histoplasma?

Yes, animals such as dogs and cats can develop histoplasmosis, usually through exposure to contaminated soil. Symptoms in pets may include chronic weight loss, coughing, diarrhea, or lethargy (extreme fatigue or sluggishness).

Pets do not spread histoplasmosis to humans through the air. However, illness in animals can sometimes indicate there is fungus in the environment. If your pet develops these symptoms, contact a veterinarian.

Resources: