Blastomycosis: The “Soil Fungus” Infection You Breathe In Without Knowing — Why It Lingers for Weeks and How Treatment Clears It
Updated: 3 days ago
Medically reviewed by *Dr. Baraa Alnahhal, MD*. Last reviewed October 13, 2026. This content is for educational purposes and is not medical advice.
Quick Answer
Blastomycosis is an infection caused by inhaling the fungus Blastomyces from moist soil or rotting wood, mostly in parts of North America. It does not spread between people. Symptoms include fever, cough and skin sores, though about half of infected people have none [1] [2]. Antifungal medication treats it, and survival is over 90% for most people [1].
What the research says
Itraconazole is the first-line drug, and alternatives are for special cases. In a multicenter cohort of 144 adults with proven or probable blastomycosis (119 treated with itraconazole and 25 with voriconazole as complete or partial therapy), voriconazole was mostly chosen for central nervous system involvement or intolerance to other azoles, and after statistical weighting there was no significant difference in treatment response between the two (Schanz et al., J Fungi, 2026) [6].
Treatment depends on severity. A clinical review explains that pulmonary disease is the most common form, ranging from mild, self-limited infection to severe, potentially fatal acute respiratory distress syndrome; amphotericin B is used first when the disease is severe, involves the central nervous system, or the person is immunosuppressed, while itraconazole is recommended for mild to moderate infection and as follow-on therapy (Schwartz and Kauffman, Semin Respir Crit Care Med, 2020) [5].
Every symptomatic case should be treated. A second review notes the fungus is hyperendemic near the Great Lakes and along the St. Lawrence, Mississippi, and Ohio rivers, that culture is required for a definitive diagnosis, and that treatment should be given to all symptomatic cases to prevent progression or recurrence (Mazi et al., Infect Dis Clin North Am, 2021) [4].
What Is Blastomycosis?
Blastomycosis is an infection caused by breathing in the fungus Blastomyces. This fungus lives in dirt or rotting wood, usually in areas near water [1], and it is too small to see. Because you cannot spot it, you can breathe it into your lungs without knowing it is there. Once inside, it can grow and make you sick, and it sometimes spreads from the lungs to the skin or other parts of the body.
The illness used to be called Gilchrist disease or Chicago disease [1], names that reflect where it was first identified. Unlike the umbrella-shaped mushrooms you can pick off the forest floor, Blastomyces is the kind of fungus you will never notice, until it causes symptoms.
Key Fact | What the Research Shows |
|---|---|
What causes it | The microscopic fungus Blastomyces, most often Blastomyces dermatitidis |
Where it lives | Moist soil and rotting wood near water, especially along riverbeds |
How you get it | Breathing in the fungus from disturbed soil |
Does it spread between people? | No, it is not contagious |
Will it go away on its own? | No, treatment with antifungal medication is required |
Where Does the Fungus Live?
Blastomyces likes to live near water, particularly in or along riverbeds. It is found in many parts of the world, but it is most common in specific regions of North America, especially the areas around the Ohio and Mississippi Rivers, the Great Lakes, and the Saint Lawrence River [1] [2]. The table below summarizes where the fungus shows up most often.
Region | Details |
|---|---|
Midwestern U.S. states | Hotspots where the infection is more common include Wisconsin and Minnesota |
South Central and Southeast U.S. states | Additional areas where the fungus is found |
U.S. Northeast | Cases have been reported here as well |
Southeastern Canada | Includes Ontario, Quebec, Manitoba, and Saskatchewan |
What Are the Symptoms of Blastomycosis?
Blastomycosis can cause a wide range of symptoms, and they often resemble the flu, which is one reason the infection is so easy to miss. The symptoms include fever, chills, fatigue, cough, shortness of breath, muscle aches, coughing up blood, night sweats, and skin sores, ulcers, bumps, or blisters [1].
The single most surprising fact about this infection is that about half of all people with blastomycosis don't have any symptoms at all [1] [2]. Many people carry the fungus in their bodies and never know it.
What Do the Skin Sores Look Like?
Blastomyces dermatitidis is the version of the fungus that most often spreads to the skin. When it does, the sores can look like large bumps, warts, or wounds. They might appear as large, open wounds or as closed clusters of bumps, and they are often scabbed or crusted over [1].
Symptom | How It Shows Up |
|---|---|
Fever | Elevated body temperature, as with the flu |
Chills | Shivering and feeling cold |
Fatigue | Unusual tiredness and low energy |
Cough | A persistent cough that lingers |
Shortness of breath (dyspnea) | Difficulty catching your breath |
Muscle aches | Soreness throughout the body |
Coughing up blood | Blood mixed with mucus from the lungs |
Night sweats | Sweating through the night |
Skin sores | Ulcers, bumps, or blisters that may be scabbed or crusted |
What Are the Complications of Blastomycosis?
The main complications are acute respiratory distress syndrome (ARDS), a serious lung emergency, and the fungus spreading from the lungs to other parts of the body. From the lungs, the fungus can move into the bloodstream and travel to the skin, bones, and the central nervous system, which includes the brain and spinal cord [1].
What Causes Blastomycosis?
Many types of the fungus Blastomyces can cause blastomycosis, but the most common culprit is Blastomyces dermatitidis (B. dermatitidis) [1].
How Do You Get It?
You get blastomycosis by breathing in Blastomyces mold from moist soil or rotting wood. Once inhaled, it can grow in the lungs and sometimes spread to other parts of the body through the blood. Outbreaks sometimes happen when large areas of soil are disturbed by construction or excavation activity, which releases fungal particles into the air [1].
An important reassurance for families and workplaces: blastomycosis is not contagious. It does not spread from person to person [1] [2], so you cannot catch it from a friend, family member, or coworker who has it.
Who Is at Higher Risk?
Anyone who lives in or travels to areas where Blastomyces is found is at risk. Your risk rises if your job or hobbies involve disrupting soil or spending time near lakes and rivers [1].
Risk Factor | Why It Raises Your Risk |
|---|---|
Construction work | Disturbs large areas of soil and dust |
Hunting | Time spent in soil and wooded areas |
Fishing | Time near rivers and lakeshores |
Camping | Exposure to soil and rotting wood outdoors |
Hiking | Disturbed ground and wooded terrain |
Veterinary work | Very rarely, a contaminated needle while treating an infected animal |
Who Is at Risk for Severe Illness?
Most cases are not severe, but certain groups face a higher risk of serious illness. You are more likely to become severely ill if you have a weakened immune system (commonly caused by HIV or by immunosuppressive medications), if you have COPD (chronic obstructive pulmonary disease) or other chronic lung conditions, or if you are older than 50 [1].
How Is Blastomycosis Diagnosed?
Diagnosing blastomycosis starts with a sample. A healthcare provider might take a sample of your blood, urine (pee), or sputum, the mucus you cough up from your lungs. If you have skin ulcers, they might also take a tissue sample, called a biopsy, from one of the ulcers [1].
The lab then runs several kinds of tests to find the fungus.
Diagnostic Step | What It Does |
|---|---|
Fungal culture | Grows Blastomyces from the sample; the best way to diagnose, but it can take several weeks |
PCR technology | Identifies Blastomyces DNA in a tissue or body-fluid sample |
Antigen or antibody tests | Look for signs of Blastomyces (antigens or antibodies) in your body |
Chest X-rays or CT scans | Let the provider look at the inside of your lungs |
Because the culture can take several weeks, your provider might start treating you before the results come back [1].
How Can You Tell If It's Blastomycosis and Not Pneumonia?
Blastomycosis can look similar to other diseases, including pneumonia. One practical clue: you might suspect blastomycosis if you've completed a course of antibiotics and you're still sick [1]. Antibiotics treat bacteria, not fungus, so an infection that survives antibiotics may be fungal.
It also helps to share your geography and lifestyle with your provider. Tell them if you live near or have traveled to areas where Blastomyces lives, or if your job or hobbies involve working with or disturbing soil.
How Is Blastomycosis Treated?
Providers treat blastomycosis with antifungal medications. The two main drugs are amphotericin B (amB) and itraconazole [1] [2]. In some cases, providers may also prescribe corticosteroids to reduce inflammation.
The illness does not go away on its own. Most people need antifungal medication for several weeks. Treatment can stretch to a year or longer for people who are severely ill, whose fungus has spread beyond the lungs, who have chronic lung disease, or who have a compromised immune system [1].
What Is the Outlook?
The survival rate for blastomycosis in most people is over 90% [1]. However, chronic lung conditions and diseases that compromise your immune system can put you at a higher risk for life-threatening illness. The complications to watch for are ARDS and spread of the fungus to the skin, bones, brain, and spinal cord.
Medical emergency: Go to the emergency room if you develop a high fever over 103°F (40°C), severe or sudden shortness of breath, chest pain, coughing up blood, confusion or other mental changes, seizures, or blue skin, lips, or nails (cyanosis) [1].
Can Blastomycosis Be Prevented?
If you live in an area where the fungus is common, it is hard to avoid breathing it in entirely. The infection is not completely preventable, but two practical steps reduce your risk.
Prevention Step | How It Helps |
|---|---|
Avoid disturbing large areas of dirt and dust, especially near water | Limits the amount of fungus released into the air you breathe |
Wear an N95 (or KN95) respirator mask when your job or hobbies expose you to soil likely to contain Blastomyces | Helps filter the air you breathe |
A common worry is whether the fungus can follow you home. It is unlikely that Blastomyces is in your house, except in dirt brought in on clothing. Because the fungus grows on rotting wood and moist soil, it would not survive on your clothes after you wash them [1].
What is the bottom line on blastomycosis?
Blastomycosis is a fungal lung infection that hides in plain sight, in the soil near rivers and lakes that hikers, hunters, and workers disturb every day. About half of infected people never feel a thing, and for the rest, it mimics a stubborn flu. It never clears up on its own, but weeks of antifungal medication treat it effectively, and the survival rate for most people exceeds 90% [1]. If flu-like symptoms, cough, or shortness of breath linger beyond a week, see a healthcare provider, and mention where you live, where you travel, and what you do for fun.
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Frequently Asked Questions
What is blastomycosis?
Blastomycosis is an infection caused by breathing in the fungus Blastomyces, which lives in moist soil and rotting wood, usually near water. The fungus grows in the lungs and can cause flu-like symptoms, and it sometimes spreads to the skin or other organs.
Is blastomycosis contagious?
No. Blastomycosis does not spread from person to person. You get it by breathing in the fungus from the environment, not from other people.
Where is blastomycosis most common?
The fungus is most common in North America, especially in areas around the Ohio and Mississippi Rivers, the Great Lakes, and the Saint Lawrence River. In the U.S., hotspots include Wisconsin and Minnesota, and cases also occur in the South Central and Southeast states and the Northeast. It is also found in southeastern Canada.
What are the symptoms of blastomycosis?
Symptoms include fever, chills, fatigue, cough, shortness of breath, muscle aches, coughing up blood, night sweats, and skin sores, ulcers, bumps, or blisters. About half of infected people have no symptoms at all.
Why does blastomycosis look like the flu?
The fungus grows in the lungs, so its early symptoms (fever, chills, fatigue, cough, muscle aches) closely resemble flu-like illness. It is often mistaken for pneumonia, especially when symptoms don't improve after antibiotics.
Can blastomycosis spread to other parts of the body?
Yes. From the lungs, the fungus can move into the bloodstream and spread to the skin, bones, and the central nervous system (brain and spinal cord).
Who is most at risk of getting blastomycosis?
Anyone who lives in or travels to areas where Blastomyces is found is at risk. Risk is higher for people whose jobs or hobbies disturb soil or involve time near lakes and rivers, such as construction workers, hunters, anglers, campers, and hikers.
Who is at risk of severe blastomycosis?
People with a weakened immune system (from HIV or immunosuppressive medications), those with COPD or other chronic lung conditions, and adults older than 50 face a higher risk of severe illness.
How is blastomycosis diagnosed?
A provider takes samples of blood, urine, sputum, or skin tissue and sends them to a lab for culture, PCR testing, or antigen and antibody testing. Chest X-rays or CT scans may be used to look inside the lungs. Culturing the fungus, the best diagnostic method, can take several weeks.
How long does blastomycosis treatment take?
Most people need antifungal medication for several weeks. Treatment may last a year or longer for people who are severely ill, have fungus spread beyond the lungs, have chronic lung disease, or have a weakened immune system.
What medications treat blastomycosis?
Providers use antifungal treatments such as amphotericin B (amB) and itraconazole. In some cases, corticosteroids are also given to reduce inflammation.
What is the survival rate for blastomycosis?
For most people, the survival rate is over 90%. Chronic lung conditions and immune-compromising diseases raise the risk of life-threatening illness.
When should I see a healthcare provider about possible blastomycosis?
See a provider if you have flu-like symptoms, cough, or shortness of breath that aren't improving after a week or are getting worse. Mention any exposure to soil near water, or travel to areas where the fungus is found.
When should I go to the emergency room?
Go to the ER for a fever over 103°F (40°C), severe or sudden shortness of breath, chest pain, coughing up blood, confusion or mental changes, seizures, or blue skin, lips, or nails (cyanosis).
Can blastomycosis be in my house?
It is unlikely, except in dirt brought in on clothing. The fungus grows on rotting wood and moist soil and would not survive on clothes after they are washed.
Related Reading
Fungal Infections (Mycosis): Symptoms, Causes, Diagnosis, Treatment and Outlook: what fungal infections are and how they're treated
Pneumonia: Complete Guide to Symptoms, Causes, and Treatment: when a lung infection goes deeper than a bad cold
Sources
Cleveland Clinic. Blastomycosis. Cleveland Clinic. Updated October 30, 2024. https://my.clevelandclinic.org/health/diseases/blastomycosis
Centers for Disease Control and Prevention. Clinical Overview of Blastomycosis. CDC. Updated April 24, 2024. https://www.cdc.gov/blastomycosis/hcp/clinical-overview/index.html
Centers for Disease Control and Prevention. Data and Statistics on Blastomycosis. CDC. Updated April 24, 2024. https://www.cdc.gov/blastomycosis/data-research/statistics/index.html
Mazi PB, et al. Blastomycosis. Infect Dis Clin North Am. 2021;35(2):515-530. PMID 34016289. https://doi.org/10.1016/j.idc.2021.03.013
Schwartz IS, et al. Blastomycosis. Semin Respir Crit Care Med. 2020;41(1):31-41. PMID 32000282. https://doi.org/10.1055/s-0039-3400281
Schanz CC, et al. A Retrospective, Comparative Cohort Analysis of the Utilization of Voriconazole-Containing Regimens Versus Itraconazole in the Treatment of Blastomycosis. J Fungi (Basel). 2026;12(4):279. PMID 42042373. https://doi.org/10.3390/jof12040279
Medical Disclaimer
This article is for general informational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition.
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