Blastomycosis: Understanding This Fungal Infection
Health ConditionsInfectious Diseases

What Is Blastomycosis? Symptoms, Causes, Diagnosis, Treatment, and Prevention

Learn more about this rare fungal infection, including why it’s becoming more widespread, what it looks like on skin, and how to prevent it.
What Is Blastomycosis? Symptoms, Causes, Diagnosis, Treatment, and Prevention
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Published on March 13, 2024
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Blastomycosis is a rare and dangerous infection caused by the fungus Blastomyces. This organism lives in natural environments, especially in moist soil and decomposing wood and leaves.

People can get blastomycosis by inhaling microscopic spores released into the air when soil containing the fungus is disturbed — for example, during digging or construction.

Blastomycosis was responsible for the death of a 29-year-old Michigan chef named Ian Pritchard in February 2024, bringing national attention to its threat.

In the United States, blastomycosis has traditionally been a concern for people in the Midwest, the Great Lakes, the South Central region, and Southeastern states (especially in the Ohio and Mississippi River valleys), says Mark Rupp, MD, the chief of the division of infectious diseases and a professor of medicine at the University of Nebraska Medical Center in Omaha.

But recently, the fungal infection has been showing up in unexpected parts of the country. “There have been some reports up in the Northeast, an area where blastomycosis hadn’t been identified before, and so we’re realizing the range of this particular fungus is probably broader than had previously been defined,” says Dr. Rupp.

Increases in temperature and precipitation because of climate change may be expanding the areas where fungi, including the fungus that causes blastomycosis, are able to survive, according to the Centers for Disease Control and Prevention (CDC).

Blastomycosis Risk Factors

Certain factors can increase a person’s risk of developing blastomycosis, including:

Geographic location: Anyone can get blastomycosis if they live in an area where Blastomyces is present.

Outdoor activities: Construction, excavation, and other activities that disturb the soil and throw dirt up into the air can increase the risk of exposure, as can outdoor recreational activities like hunting and camping.

Race or ethnicity: Some ethnicities or races (non-white) may be at higher risk for hospitalization with blastomycosis.

Health conditions and situations: Certain health conditions and situations can raise the risk of severe blastomycosis, including:

  • Advanced AIDS (late-stage HIV infection)
  • Living with an organ transplant
  • Taking corticosteroids or TNF-inhibitors (which suppress the immune system)
  • Pregnancy
Typically, blastomycosis isn’t thought of as a communicable disease, meaning it doesn’t spread from person to person, says Rupp. In extremely rare cases, blastomycosis has spread between people via needlestick injuries, bites, or sexual contact, according to the CDC.

Symptoms of Blastomycosis

About half of people who are infected with Blastomyces develop symptoms, which can vary widely from person to person, says Rupp.

Blastomycosis may result in respiratory and flu-like symptoms such as:

  • Fever
  • Cough
  • Shortness of breath
  • Night sweats
  • Muscle aches or joint pain
  • Weight loss
  • Chest, rib, or back pain
  • Fatigue (extreme tiredness)

In some people, especially those at higher risk for severe illness, blastomycosis can spread and can cause infection in the bones and joints as well as the central nervous system, says Rupp.

What Does Blastomycosis Look Like on Skin?

In some cases, blastomycosis can cause skin lesions, which may appear as nodules (lumps) or ulcers (open sores).

 Skin issues are more common in severe cases or in people with compromised immune systems.

Diagnosis of Blastomycosis

Because blastomycosis shares symptoms with many other illnesses and infections, diagnosis usually involves a combination of a physical examination (including medical and travel history to assess potential exposure risks), laboratory tests, and imaging studies.

According to the CDC, people should get tested for blastomycosis if they satisfy all three of these criteria:

  • They have symptoms of pneumonia.
  • They’ve been treated with antibiotics that aren’t working.
  • In the past three weeks to three months they’ve been to an area where the fungus exists.

“This isn’t a bacterial disease where it’s rapidly progressive; blastomycosis tends to evolve over days to weeks to months, as opposed to over hours to days,” says Rupp.

Doctors may also choose to test patients who have new skin lesions or those who’ve been to an area or participated in activities that are linked to other people with a blastomycosis diagnosis.

Test for blastomycosis include:

  • Chest X-Rays Radiological imaging can reveal lung infiltrates (substances) or nodules, which would indicate pulmonary (lung) blastomycosis.
  • Sputum and Tissue Cultures Respiratory secretions like sputum (a mixture of saliva and mucus) or tissue samples can be analyzed in the lab (cultured) in order to diagnose the infection.
  • Blood Tests Tests for antibodies (immune-system responses to infection) and antigens (the things that provoke an immune response) can help doctors confirm the presence of the fungus in the body.

Treatment for Blastomycosis

Blastomycosis can be treated with a variety of antifungal medications, says Rupp.

  • Itraconazole This oral antifungal drug is often the first-line treatment for mild to moderate blastomycosis cases. A person may need to take it for several months until the infection clears.
  • Amphotericin B This antifungal is usually reserved for severe or disseminated cases (in which the fungus has spread throughout the body), especially involving immunocompromised people. Patients may initially receive amphotericin B through an IV.
The duration of antifungal therapy varies, but it takes longer than treatment for a bacterial infection, says Rupp. The length of time required to treat blastomycosis can range from a few months to over a year, depending on the severity of the infection and the person’s response to treatment.

It’s important for a person with blastomycosis to follow their healthcare provider's recommendations on treatment and follow-up, Rupp says.

Prognosis for Blastomycosis

The majority of people with blastomycosis can be successfully treated, with an estimated 80 to 95 percent of people recovering from the infection. Immunocompromised people are at a higher risk of death from blastomycosis.

Prevention of Blastomycosis

It can be difficult to completely avoid exposure to the fungus, but there are a few ways a person can reduce their risk of infection.

  • Know the high-risk areas. Stay informed about the geographic regions where blastomycosis is prevalent and take extra precautions there.
  • Wear protective clothing. When doing outdoor activities that could cause soil disturbance, wear appropriate clothing, including gloves.
  • Wear a mask. In situations where there is a higher risk of inhaling airborne spores, such as during construction or excavation work, masks can provide an additional layer of protection.
  • Limit soil exposure. Minimize direct contact with soil in high-risk areas, especially if you have open wounds or cuts on your skin.
  • Practice good hand hygiene. Wash your hands thoroughly, particularly after outdoor activities, to reduce the risk of accidentally ingesting spores.

Blastomycosis in Dogs

Blastomycosis can affect dogs, says Rupp. “There have been a number of outbreaks in dogs and in kennels,” he says. “The fungus can cause a kind of ulcerative lesion, typically on the snout — the nose and mouth.”

As with humans, blastomycosis can make dogs very ill. “It’s important for people to know that if their dog has any sort of lesions on the jaw or snout and appears to feel sick, it needs to go to the vet right away,” he says.

Common Questions & Answers

What is blastomycosis?
Blastomycosis is an infection caused by the fungus Blastomyces. It is rare but may be a growing threat as climate change increases the areas where the fungus can survive.
People get blastomycosis by breathing in spores of the fungus Blastomyces. The fungus lives in natural environments like moist soil and decomposing leaves.
Blastomycosis doesn’t typically spread from person to person, but in rare cases it has spread through needlestick injury (when the skin is accidentally punctured by a used needle), biting, or sexual contact.
Blastomycosis is sometimes deadly, especially in people who are immunocompromised, but most of those who get it can be successfully treated with antifungal medications.
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Jane Yoon Scott, MD, is an infectious disease physician and an assistant professor of medicine at Emory University in Atlanta. Dr. Scott enjoys connecting with her patients, empowering them to understand and take ownership of their health, and encouraging them to ask questions so that they can make informed and thoughtful decisions.

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Resources
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