The CDC’s New Study Exposes Mold’s Prevalent Health Risks

For years, patients raising concerns about mold have been told the same things: the risk is exaggerated, the symptoms are too vague, the connection is unproven, and serious illness only happens in a narrow group of severely immunocompromised people. 

 

That standard-care narrative has left many people feeling dismissed, minimized, and pressured to question what they are experiencing—even when their health declines after significant exposure.

 

The CDC’s newest surveillance report makes that dismissal much harder to defend. Its findings reveal that invasive mold disease is not confined to the textbook patient profile, not limited to the lungs, and not nearly as easy to rule out as conventional risk criteria suggest. This study exposes a major blind spot: mold can cause devastating health consequences, and relying on rigid assumptions about who is really at risk can delay recognition until a patient is critically ill.

 

The larger issue goes beyond the fact that mold can be dangerous. 

 

It’s that our medical system has commonly treated uncertainty as proof that the danger isn’t real. This new CDC report challenges that complacency and forces a more honest conversation about the wide-ranging impact of mold, the limits of current diagnostic frameworks, and the consequences of dismissing patients too quickly.

 

Key Takeaways

• The new CDC mold study challenges the conventional belief that invasive mold disease only affects patients with classic high-risk conditions.
• Mold exposure can lead to very different outcomes, including allergy, CIRS, colonization, and invasive disease, which require different evaluation and treatment.
• Although invasive mold disease most commonly affects the lungs, the CDC findings show that it can also involve the central nervous system and other organs.
• Corticosteroids may control inflammation while simultaneously weakening several immune defenses needed to contain fungal organisms.
• Cystic fibrosis highlights why finding mold in a respiratory specimen does not automatically distinguish harmless colonization from clinically significant disease.
• Root-cause mold care requires identifying what is driving inflammation rather than relying exclusively on symptom suppression.
• Reducing exposure, correcting water damage, supporting immune resilience, and regulating the nervous system can all play important roles in recovery.

 

 

The New CDC Hospital Surveillance Study

 

 

On July 30, 2026, the Centers for Disease Control and Prevention published a new Morbidity and Mortality Weekly Report examining invasive mold disease across four hospitals in metropolitan Atlanta, Georgia. The report, titled Active Surveillance for Invasive Mold Disease—Four Hospitals, Atlanta, Georgia, 2020–2024, analyzed five years of hospital and laboratory data collected from two academic hospitals, one community hospital, one federal hospital, and their associated outpatient clinics.

 

This was an active, laboratory-based surveillance project conducted through the Georgia Emerging Infections Program. Unlike a clinical trial testing a drug or intervention, surveillance studies are designed to identify cases, document patterns, and better understand how a disease appears within a defined population. 

 

Researchers proactively reviewed laboratory records for patients with positive mold cultures or positive Aspergillus galactomannan tests and then examined the available clinical information to determine whether each potential case represented invasive mold disease, colonization, contamination, or another explanation. 

 

The project was created to address a significant gap in public-health data. Invasive mold disease isn’t a nationally notifiable condition, meaning healthcare facilities aren’t universally required to report cases to a central national surveillance system. 

 

As a result, the US lacks comprehensive data showing how often these infections occur, which patients are affected, how frequently cases fall outside conventional risk categories, or whether rates are changing over time. Existing information has typically come from individual hospitals, outbreaks, insurance databases, or studies focused on traditionally high-risk groups rather than a broader hospital population. 

 

By actively monitoring several different hospital settings over multiple years, the CDC sought to create a more detailed picture of invasive mold disease, including patient characteristics, possible risk factors, healthcare use, treatment, and outcomes. 

 

Establishing a baseline is also important for hospitals because invasive mold infections were believed to be uncommon enough that even a small increase may signal a healthcare-associated outbreak linked to construction, ventilation, contaminated materials, or another shared exposure. The findings were intended to improve awareness and help guide future prevention, diagnosis, treatment, research, and surveillance practices. 

 

This report shouldn’t be interpreted as a measurement of mold disease across the entire US. It was limited to selected facilities in one metropolitan area; most cases came from the two academic hospitals, and the surveillance system didn’t include a children’s hospital. It also focused specifically on suspected invasive mold disease in a hospital-based population. 

 

However, the report offers an unusually detailed look at a serious category of mold-related illness that remains poorly tracked and frequently difficult to recognize. 

 

Mold Allergy, Colonization, Invasive Disease vs. CIRS

 

 

Mold exposure doesn’t produce one universal illness pattern. Depending on the intensity and duration of exposure, the mold species involved, the condition of the indoor environment, and the individual’s health, exposure may cause temporary symptoms, contribute to persistent inflammatory illness, establish colonization in damaged airways, or develop into an invasive infection.

 

Category	What It Means	What Is Happening in the Body?	Common Clinical Pattern	What Happens After Exposure Is Removed?	Evaluation and Treatment
Mold exposure	A person inhales, touches, or otherwise comes into contact with mold spores, fragments, or other materials from a damp or water-damaged environment. Exposure itself is an event and not a diagnosis.	Mold particles may irritate the eyes, skin, nose, throat, or lungs even when no allergy or infection is present. The body may mount a short-term inflammatory response to the exposure.	Eye or throat irritation, nasal symptoms, coughing, wheezing, skin irritation, or a temporary worsening of asthma or other respiratory symptoms. Some people experience no noticeable symptoms at all.	Acute irritation and exposure-related symptoms may improve substantially or resolve after leaving the environment, correcting the moisture source, and receiving appropriate supportive treatment.	Evaluation focuses on the exposure history, timing of symptoms, the building environment, and ruling out allergy, infection, or other medical causes. The primary intervention is stopping or reducing exposure and properly correcting the water damage.
Mold allergy	An allergic immune response to mold proteins or spores. The immune system recognizes mold as an allergen and releases inflammatory mediators when exposure occurs.	This is typically an IgE-mediated or hypersensitivity response. Mold doesn’t need to be growing inside the body for an allergic reaction to occur.	Sneezing, nasal congestion, runny nose, itchy or watery eyes, coughing, wheezing, rash, asthma flares, or allergic sinus symptoms. Certain patients may develop more complex allergic conditions, such as allergic bronchopulmonary aspergillosis.	Symptoms often improve when exposure is reduced, although sensitized individuals may react again with future exposure. Ongoing airway inflammation, asthma, or sinus disease may require treatment even after the original exposure ends.	Evaluation may include clinical history, allergy testing, lung-function testing, imaging, or condition-specific laboratory testing. Management may include exposure reduction, antihistamines, nasal treatments, asthma care, or other allergy-directed therapies. Mold allergy is distinct from an invasive fungal infection.
Mold illness or CIRS	Within the CIRS framework, Chronic Inflammatory Response Syndrome is a persistent, multisystem inflammatory illness that may develop in susceptible individuals following exposure to the complex mixture found in water-damaged buildings.	The innate immune system becomes dysregulated and remains chronically activated after exposure, affecting inflammatory signaling across multiple body systems.	Symptoms may involve several systems at once, including fatigue, cognitive difficulties, headaches, sleep disruption, pain, respiratory complaints, mood changes, temperature or autonomic instability, digestive symptoms, and unusual sensitivity to environments or exposures. The pattern is generally broader than a localized allergy.	This is a key distinction: Leaving the exposure is essential and may produce some improvement, but symptoms and immune dysregulation may persist after exposure has ended. In CIRS, the inflammatory response doesn’t reset on its own, so environmental removal alone may be insufficient for full recovery.	Evaluation should include a detailed exposure history, multisystem symptom pattern, assessment for competing diagnoses, and clinician-directed testing. Treatment generally begins with exposure removal but may also require additional support addressing inflammation, impaired clearance, hormonal or neurological effects, and other downstream dysfunction.
Mold colonization	Mold is present and can be growing within a body site, most commonly structurally abnormal airways, without clear evidence that it has invaded surrounding tissue or blood vessels. Mold colonization can happen in nasal passages, the gut, skin, and virtually anywhere in the body.	The organism may remain in mucus, an airway cavity, the sinuses, or any other vulnerable surface in the body. Colonization is more likely when parts of the body are compromised and/or normal clearance is impaired, as may occur with cystic fibrosis, bronchiectasis, chronic lung disease, or preexisting lung cavities.	Colonization may produce no symptoms, contribute to chronic respiratory complaints, or coexist with allergic or chronic fungal disease. Colonization symptoms can vary drastically depending on which part of the body is colonized (e.g., gut, skin, nasal passages). A positive culture alone can’t determine whether the mold is merely present or causing tissue damage.	Removing environmental exposure can reduce additional fungal burden, but established colonization may not disappear simply because the person leaves a moldy building. The underlying condition and the clinical significance of the organism must also be addressed.	Evaluation may involve repeated cultures, imaging, bronchoscopy, allergy markers, fungal biomarkers, and the overall clinical picture. Treatment is individualized and further varies based on what’s colonized. Colonization is distinct from invasive infection but can complicate diagnosis and may coexist with allergic disease.
Invasive mold disease	A serious fungal infection in which mold grows into blood vessels, deep tissues, or internal organs. The lungs are a common starting point, but disease may spread to the brain, skin, bones, or other sites.	Mold spores germinate, and fungal structures invade tissue, sometimes entering blood vessels and causing tissue destruction, bleeding, clotting, or dissemination to other organs. This is a true infection rather than an allergic or inflammatory response alone.	Fever, cough, chest pain, shortness of breath, rapidly worsening pneumonia, sinus or facial symptoms, skin lesions, neurological changes, or signs of organ involvement. Presentation depends on the site and may be difficult to distinguish from bacterial or viral illness.	Exposure removal is important, but it is not sufficient once tissue invasion has occurred. Invasive disease can progress even after the original exposure ends and requires urgent medical treatment.	Diagnosis may require imaging, cultures, fungal biomarkers, bronchoscopy, tissue biopsy, histopathology, or molecular testing. Treatment generally involves systemic antifungal medication and, in some cases, surgery.

 

 

These outcomes can share symptoms, occur at the same time, and all begin with contact with mold, but they involve very different biological processes and levels of risk. Understanding these distinctions is critical because they don’t mean the same thing or require the same treatment. These categories aren’t always neatly separated either. A person may be exposed without becoming sick, have both mold allergy and airway colonization, or experience persistent inflammation without evidence that viable mold is invading tissue. 

 

Someone with chronic lung disease may also move along a spectrum from colonization to allergic or chronic fungal disease, while another patient may be vulnerable to invasive infection. A positive environmental test, urine mycotoxin result, nasal culture, or respiratory culture therefore can’t identify the category by itself.

 

The difference between a temporary exposure-related illness and CIRS is also important. In an acute response, the immune system reacts to an environmental trigger and generally settles once the exposure is removed, the body clears the irritants, and any resulting allergy or inflammation is treated. 

 

In CIRS, the problem is that the immune response remains dysregulated after the person is no longer in the environment. Exposure removal is still the nonnegotiable first step, but it may not reverse the inflammatory cascade, neurological effects, hormonal changes, or other downstream dysfunction that developed while the person was exposed.

 

None of these distinctions make environmental removal less important. Reducing ongoing exposure is relevant for all cases. What changes is the type of treatment and care required. 

 

Invasive Mold Disease Surveillance, Findings, and Outcomes

 

 

One of the most important findings in the CDC’s hospital surveillance report wasn’t the 45% 90-day mortality rate, although that number alone shows how devastating invasive mold disease can be. 

 

The more revealing finding was that 35% of the patients classified as having invasive mold disease didn’t have the formal Mycoses Study Group host factors traditionally associated with these infections. In other words, more than one in three cases occurred outside the classic risk profile clinicians are typically taught to expect.

 

Between 2020 and 2024, the surveillance system identified 968 patients with potential invasive mold disease across four Atlanta-area hospitals and associated outpatient clinics. Potential cases were initially flagged through either a positive mold culture or a positive Aspergillus galactomannan test, a biomarker used to help detect Aspergillus. Researchers then reviewed laboratory results, imaging, pathology, clinical findings, underlying risk factors, physician assessments, antifungal treatment, and patient outcomes to determine whether each finding represented invasive disease rather than colonization, contamination, or another noninvasive condition. 

 

Of the 968 potential cases reviewed, 449 patients, 46% were ultimately classified as having invasive mold disease. 

 

The fact that fewer than half of all positive findings were classified as invasive disease reinforces an important distinction: limiting recognition only to patients who fulfill the most restrictive research criteria can also miss clinically serious cases.

 

How the CDC Classified the Cases

The 449 invasive mold disease cases were divided into three categories:

 

• 89 cases, or 20%, were MSG-proven. These patients had stronger direct evidence of tissue invasion, such as mold cultured from a normally sterile body site or histopathology showing mold invading tissue or blood vessels.
• 142 cases, or 32%, were MSG-probable. These cases met a combination of mycological evidence, compatible clinical or imaging findings, and at least one recognized host factor.
• 218 cases, or 49%, were surveillance cases. These patients didn’t fulfill all the MSG criteria for proven or probable disease, but clinicians diagnosed suspected invasive mold disease and initiated mold-active antifungal treatment, or the patient died within three days of specimen collection before treatment could reasonably be started. 

 

This additional surveillance category was significant. Nearly half of the classified cases wouldn’t have fit neatly into the conventional proven or probable definitions, yet clinicians considered the disease serious enough to treat, or the patient deteriorated too quickly for treatment to begin.

 

MSG definitions were developed primarily to create consistent and highly specific case definitions for clinical studies. That is valuable for research, but these criteria weren’t intended to function as a rigid bedside rule-out system. A patient can fall outside a formal research definition and still have a clinically concerning invasive mold infection.

 

More Than One in Three Cases Lacked Classic Host Factors

 

 

Formal MSG host factors include vulnerabilities such as prolonged severe neutropenia, hematologic cancer, solid-organ or stem-cell transplantation, certain major immunosuppressive medications, severe inherited immunodeficiency, and prolonged systemic corticosteroid exposure.

 

Among the 449 invasive mold disease cases, 292 patients had at least one MSG host factor, but 157 patients, or 35%, did not. 

 

This doesn’t mean that all 157 patients were completely healthy before becoming ill. Some had critical illness, lymphopenia, chronic lung disease, kidney disease, recent viral infections, shorter immunosuppressive exposures, or other vulnerabilities that weren’t fully captured by the formal MSG host-factor list. 

 

For example, 60% of all invasive mold disease patients had documented lymphopenia, 41% had chronic pulmonary disease, and many had experienced significant healthcare use or severe illness around the time the mold was detected. 

 

The distinction matters because it means the existing framework didn’t fully describe the range of people who developed serious disease.

 

Aspergillus and Pulmonary Disease Dominated the Findings

 

 

Among the 449 classified cases:

 

• 71% involved Aspergillus
• 68% involved the pulmonary system
• 11% involved cutaneous or deep tissue
• 10% involved the sinuses, nose, or face
• 9% involved the central nervous system
• 9% affected more than one body site

 

The lungs were the most commonly affected site, which is consistent with mold spores generally entering the body through inhalation. 

 

However, the findings also show why invasive mold disease shouldn’t be viewed as exclusively respiratory. It can involve the sinuses, skin, deep tissues, bones, blood, eyes, and central nervous system. Among patients with disease at multiple sites, the most common combination was pulmonary and central nervous system involvement. 

 

The predominance of Aspergillus is also clinically relevant. Aspergillus is common in indoor and outdoor environments, and most people inhale its spores without developing invasive disease. When immune defenses, lung clearance, or tissue containment are compromised, however, the spores may germinate and invade surrounding tissue or blood vessels.

 

Many Patients Were Already Critically Ill

 

 

The healthcare-use data demonstrate the severity of illness surrounding these cases:

 

• 43% had been admitted to an intensive care unit during the 14 days before the incident mold specimen was collected.
• 50% were in an ICU on the specimen date or during the following 13 days.
• 50% received invasive mechanical ventilation during the 30 days before or on the specimen date.
• 83% were hospitalized on the specimen date or within the following six days. 

 

Some patients may have developed mold disease because they were already critically ill, while in others the infection may have triggered or contributed to respiratory failure, worsening organ function, or clinical decline. The surveillance design can identify these associations but can’t determine the direction of causation in every individual case.

 

What the data do establish is that invasive mold disease frequently appeared in the setting of profound illness.  

 

Mortality Remained High Despite Treatment

 

 

Most patients were treated aggressively. 81% of patients received at least one mold-active antifungal medication, and one third received more than one antifungal. Common treatments included isavuconazole, voriconazole, amphotericin B, echinocandins, and posaconazole. 

 

Despite this:

 

• 10% died within three days of the incident specimen collection.
• 30% died in the hospital.
• 45% died within 90 days among the cases with complete mortality follow-up. 

 

The 90-day figure requires an important qualification. It was all-cause mortality, meaning the study didn’t establish that mold was the sole or direct cause of every death. The calculation included 349 cases from 2020 through 2023 and excluded 2024 cases because post-discharge death-registry data weren’t complete yet. Of those 349 evaluable patients, 157 died within 90 days. 

 

Even with that context, the mortality rate remains deeply concerning. High mortality despite frequent antifungal treatment may reflect delayed recognition, rapidly progressive tissue invasion, severe underlying illness, infection in difficult-to-treat sites, limited diagnostic sensitivity, antifungal resistance, medication toxicity, or the relatively small number of available antifungal drug classes.

 

Notably, mortality was relatively similar across the three case classifications: 42% in MSG-proven cases, 49% in MSG-probable cases, and 44% in surveillance cases. This is significant because it suggests that the broader surveillance category wasn’t merely capturing mild or inconsequential mold findings. Patients who fell outside the strict proven and probable definitions still experienced severe outcomes.

 

Pro-Tip: Antifungal treatment can be highly controversial in the CIRS-Shoemaker space. In our clinical practice, they can play an important role in individualized CIRS care when timed appropriately, and should be considered higher priority for more aggressive colonization and invasion cases.   

 

The Larger Clinical Warning

 

 

The warning is that clinicians are likely relying on an incomplete picture of who is vulnerable. When a substantial percentage of patients with severe disease falls outside the profile used to recognize that disease, the framework must be questioned rather than the patients dismissed.

 

Classic risk factors should increase suspicion, but their absence shouldn’t automatically end the investigation. Research criteria can improve consistency, but when they are treated as absolute clinical boundaries, they can also create dangerous blind spots.

 

Mold and the Nervous System

 

 

Although mold is commonly framed as a respiratory threat, invasive disease can also affect the central nervous system, where the consequences may become far more widespread and severe.

 

What Is the Central Nervous System?

 

 

The central nervous system (CNS) consists of the brain and spinal cord and serves as the body’s primary control and communication center. It receives and processes information, coordinates movement and sensation, and helps regulate cognition, mood, balance, breathing, heart rate, digestion, and other essential functions. 

 

Since it influences nearly every major body system, problems affecting the CNS can produce symptoms that appear widespread or seemingly unrelated.

 

CDC Surveillance Study Findings

 

 

Of the 449 patients classified as having invasive mold disease, 41 patients, approximately 9%, had central nervous system involvement. The CDC reported the CNS separately from eye infections, meaning this category referred specifically to invasive disease involving structures such as the brain, spinal cord, or surrounding tissues—not visual symptoms, general neurological complaints, or cognitive changes attributed to mold exposure. 

 

The CNS cases were also more heavily represented within the CDC’s stricter diagnostic classifications. CNS involvement was documented in 19 of the 89 MSG-proven cases, 17 of the 142 MSG-probable cases, and five of the 218 broader surveillance cases. Put another way, nearly half of the CNS cases were classified as proven invasive disease, which required direct evidence such as mold recovered from a normally sterile site or histopathology demonstrating fungal invasion and associated tissue damage. 

 

This gives the CNS finding more clinical weight than a report based solely on nonspecific neurological symptoms or a history of environmental exposure. 

 

For probable cases, CNS involvement could be supported by characteristic imaging findings, such as a lesion seen on head CT or meningeal enhancement, alongside mycological evidence and a recognized host risk factor. The broader surveillance category captured patients who didn’t meet every formal MSG criterion but whose clinicians still diagnosed and treated invasive mold disease, or who died shortly after specimen collection before treatment could be initiated. 

 

The lungs remained the most commonly affected site, but the documented CNS cases show that invasive mold can extend into areas where diagnosis and treatment become significantly more complex. 

 

Central Nervous System Mold Symptoms

 

 

When invasive mold disease reaches the central nervous system, symptoms can vary depending on the location and severity of the infection and may resemble meningitis, a brain abscess, or a stroke. Possible symptoms include:

 

• Persistent or severe headache
• Fever
• Neck pain or stiffness
• Nausea or vomiting
• Sensitivity to light
• Dizziness or vertigo
• Unsteady walking, poor balance, or loss of coordination
• Confusion, disorientation, memory problems, or difficulty thinking clearly
• Unusual drowsiness, lethargy, or reduced alertness
• Changes in behavior, personality, or mental status
• Seizures
• Muscle weakness or numbness, particularly on one side
• Facial drooping or asymmetry
• Difficulty speaking or understanding speech
• Changes in vision or abnormal eye movements
• Difficulty swallowing
• Loss of bladder or bowel control
• Sudden stroke-like symptoms
• Fainting, loss of consciousness, or coma in severe cases

 

These symptoms aren’t specific to mold and can indicate several medical emergencies. Sudden neurological changes, seizures, severe headache, confusion, or loss of consciousness require immediate evaluation. 

 

How Mold Can Affect the Central Nervous System

 

 

Mold can impact the central nervous system (CNS) from three routes:

 

From the lungs: Most invasive mold infections begin when spores are inhaled into the lungs. In a susceptible person, molds such as Aspergillus can germinate, invade lung tissue and blood vessels, and enter the bloodstream. The infection may then travel to distant organs, including the brain and tissues surrounding the spinal cord. This bloodstream route, called hematogenous dissemination, is one of the primary ways invasive mold reaches the central nervous system. 

 

From the sinuses: Invasive mold disease can also begin in the nasal passages or paranasal sinuses, particularly with Aspergillus or molds that cause mucormycosis. Because the sinuses sit close to the eyes, skull base, and brain, an aggressive infection may spread directly through nearby tissue, bone, blood vessels, or the structures surrounding the eye. This allows mold to enter the CNS without first spreading through the bloodstream from the lungs. 

 

Inside the CNS: Once mold enters the central nervous system, it can invade tissue and the walls of blood vessels. This angioinvasion may obstruct blood flow, promote clots, damage vessel walls, and cause areas of infarction, bleeding, or tissue death. The infection may form one or more brain abscesses or involve the membranes and fluid surrounding the brain and spinal cord, resulting in fungal meningitis. 

 

Mold and Nervous System Dysregulation

 

 

Mold exposure can contribute to nervous system dysregulation by repeatedly activating inflammatory and immune pathways that communicate directly with the brain. These signals interact with the autonomic nervous system and the hypothalamic-pituitary-adrenal stress axis, potentially shifting the body toward a sympathetic, or fight-or-flight, state. 

 

In susceptible individuals, particularly those experiencing persistent inflammation within a CIRS-type pattern, the brain may continue interpreting internal symptoms and environmental cues as signs of danger even when there is no immediate emergency. Experimental research supports a connection between repeated mold exposure, innate immune activation, and changes in fear-related brain responses. 

 

Over time, inflammation, poor sleep, pain, breathing difficulty, unpredictable symptoms, and fear of re-exposure can reinforce one another. The nervous system becomes more reactive, ordinary sensations may trigger an exaggerated alarm response, and the body can struggle to return to its normal rest-and-digest state. The immune system, brain, and autonomic nervous system continuously influence one another. 

 

The result can be a self-perpetuating cycle in which physical illness drives threat signaling, while prolonged fight-or-flight activation further disrupts sleep, digestion, pain tolerance, cardiovascular regulation, and recovery. 

 

Important Note: Active mold infection, colonization, or invasion in the central nervous system (CNS) isn’t the same as nervous system regulation. Both require proper management and different treatment modalities for effective care, and may overlap in many cases. Nervous system regulation can support recovery but should never be used to imply that any mold-related condition is psychological. The most comprehensive plan combines appropriate conventional treatment with an investigation of exposure, immune function, metabolic health, tissue integrity, medication risks, and persistent inflammatory signaling. 

 

Corticosteroid Medications and Fungal Susceptibility

 

 

The CDC surveillance framework recognizes prolonged corticosteroid use as a formal host factor for invasive mold disease, using a threshold of at least 20 mg of prednisone-equivalent medication daily for more than 21 days within the previous 60 days. This generally refers to systemic steroid exposure; topical steroids typically don’t meet the criterion, while inhaled and nasal steroids usually have less systemic impact at standard doses.

 

Corticosteroids can be powerful tools for controlling inflammation, but their immune-suppressing effects may also reduce the body’s ability to contain and eliminate fungal organisms.

 

What Is a Corticosteroid?

 

 

Corticosteroids are medications designed to mimic cortisol, a steroid hormone naturally produced by the adrenal glands. They reduce inflammation and modify immune-system activity, and are commonly used in standard care for treating a variety of inflammatory illnesses. 

 

Corticosteroids may be taken orally, injected, inhaled, applied to the skin, or used as nasal sprays, with their systemic effects varying by the medication, dose, route, and treatment duration. They are different from anabolic steroids, which are associated with testosterone and muscle growth. 

 

Why Corticosteroids Are Prescribed

 

 

Since corticosteroids quickly reduce inflammation and suppress immune activity, they are used across many areas of medicine. Common reasons they may be prescribed include:

 

• Respiratory conditions: Asthma flares, COPD exacerbations, croup, sarcoidosis, and other inflammatory lung diseases
• Severe allergic reactions: Anaphylaxis follow-up care, serious medication reactions, hives, angioedema, and severe allergy symptoms
• Autoimmune and rheumatic diseases: Rheumatoid arthritis, lupus, vasculitis, polymyalgia rheumatica, inflammatory muscle diseases, and acute gout
• Skin conditions: Eczema, contact dermatitis, psoriasis, severe rashes, and autoimmune blistering disorders
• Digestive and liver conditions: Crohn’s disease, ulcerative colitis, autoimmune hepatitis, and other inflammatory gastrointestinal diseases
• Neurological conditions: Multiple sclerosis relapses, autoimmune neurological disorders, and swelling affecting the brain or spinal cord
• Brain swelling: Cerebral edema caused by tumors, surgery, injury, or other conditions in which inflammation increases pressure within the skull
• Eye conditions: Uveitis, optic neuritis, and other inflammatory eye diseases
• Kidney and blood disorders: Nephrotic syndrome, inflammatory kidney disease, immune thrombocytopenia, and autoimmune hemolytic anemia
• Hormone deficiencies: Adrenal insufficiency, Addison’s disease, and other conditions in which the body does not produce enough natural corticosteroid hormones
• Cancer care: Certain leukemias, lymphomas, multiple myeloma, cancer-related swelling, and management of some treatment side effects
• Organ transplantation: Preventing or treating rejection by suppressing immune activity
• Joint and soft-tissue inflammation: Arthritis, bursitis, tendon inflammation, and localized pain treated with corticosteroid injections
• Severe COVID-19: Hospitalized patients who require supplemental oxygen or respiratory support, where excessive inflammation is contributing to lung injury
• Other serious infections in select situations: As an adjunct to antimicrobial treatment—not as a stand-alone treatment—for conditions such as bacterial meningitis or certain severe pneumonias

 

How Steroids Raise Fungal Risk

 

 

Corticosteroids don’t create mold or directly cause fungal infections. Instead, they suppress several overlapping immune defenses that normally recognize inhaled spores, contain fungal growth, and destroy the larger hyphae that develop when spores germinate. 

 

The degree of risk depends on the steroid dose, duration, delivery method, underlying illness, blood-sugar control, and use of other immune-suppressing medications.

 

Macrophages Lose First-Line Effectiveness

 

 

Macrophages are among the first immune cells to encounter mold spores after they enter the lungs. They recognize the spores, engulf them through phagocytosis, generate inflammatory signals, and recruit additional immune cells to the area. Corticosteroids can weaken this early response by reducing fungal recognition, inflammatory signaling, immune-cell recruitment, phagocytosis, and intracellular killing. 

 

Experimental research has shown that glucocorticoid exposure can reduce macrophages’ ability to prevent Aspergillus spores from germinating, partly by suppressing the oxidative mechanisms used to kill engulfed spores. When this first-line cleanup system is impaired, inhaled spores have more opportunity to persist, swell, germinate, and begin forming invasive hyphae. 

 

Neutrophils and T-Cells Become Less Effective

 

 

Neutrophils provide another critical layer of protection, particularly after fungal spores develop into hyphae. Corticosteroids can impair their ability to migrate into infected tissue, generate an oxidative burst, release antifungal enzymes through degranulation, and damage or contain growing hyphae. Recent experimental research found that dexamethasone suppressed neutrophil control of invasive Aspergillus hyphal growth, allowing more extensive fungal invasion. 

 

Steroids can also suppress T-cell activation, proliferation, and cytokine production, including Th1-type signals such as interferon-gamma that help coordinate macrophages, neutrophils, and other antifungal defenses. 

 

Research examining Aspergillus-specific immunity found that steroid treatment reduced both T-cell proliferation and interferon-gamma release. This weakens communication between the adaptive and innate immune systems and makes it harder to sustain a coordinated response. 

 

Importantly, a normal or even elevated neutrophil count on routine bloodwork doesn’t guarantee that those cells are functioning effectively where the infection is occurring. A blood count measures how many neutrophils are circulating, but it doesn’t measure whether they can reach the affected tissue, produce an adequate oxidative response, degranulate normally, or damage fungal hyphae during corticosteroid use.

 

Steroids Change the Terrain

 

 

Beyond suppressing specific immune cells, corticosteroids can change the body’s metabolic and tissue environment in ways that make fungal control more difficult. These changes may create more favorable conditions for fungal persistence, germination, and tissue invasion—especially when several vulnerabilities occur at the same time.

 

Hyperglycemia: Corticosteroids increase glucose production by the liver while reducing the body’s sensitivity to insulin, which can raise blood sugar or worsen existing insulin resistance. Hyperglycemia can interfere with neutrophil movement, phagocytosis, complement activity, and other defenses needed to recognize and control fungal organisms. This risk is especially relevant for people with diabetes, prediabetes, or poor glucose control before steroid treatment begins. 

 

Reduced containment: Inflammation isn’t always harmful; a controlled local inflammatory response helps recruit immune cells and contain an organism before it spreads. By dampening cytokine signaling, immune-cell recruitment, and coordinated tissue-level defense, corticosteroids can weaken this localized walling-off response. If inhaled spores escape early clearance, reduced containment may give them more opportunity to germinate, form hyphae, penetrate surrounding tissue, and potentially spread beyond the original site. 

 

Tissue and barrier effects: Prolonged corticosteroid exposure can thin the skin, reduce fibroblast activity and collagen production, weaken barrier function, and delay wound and tissue repair. Depending on the route and duration of treatment, mucosal defenses may also become more vulnerable. When physical barriers are weakened and damaged tissue repairs more slowly, fungi may have more opportunity to remain at a surface or invade deeper tissue. 

 

These pressures can compound one another. A patient with diabetes, damaged airways, critical illness, a recent viral infection, or additional immunosuppressive treatment may face substantially greater risk than someone taking the same steroid dose without those vulnerabilities. Fungal susceptibility isn’t shaped by one medication in isolation, but by the total terrain in which exposure and immune defense meet.

 

The Connection Between Mold Colonization and Cystic Fibrosis

 

 

Another relevant context from the CDC surveillance study was that cystic fibrosis creates airway conditions that can make mold colonization more likely. 

 

What Is Cystic Fibrosis?

 

 

Cystic fibrosis (CF) is an inherited genetic disorder that disrupts the movement of salt and water across cell surfaces, causing mucus to become unusually thick and sticky. This mucus can obstruct the airways, impair the lungs’ natural clearance mechanisms, trap bacteria and other organisms, and contribute to repeated infections and progressive lung damage. 

 

CF also commonly affects the pancreas and digestive system by interfering with the release of enzymes needed to digest food and absorb nutrients. Although there is currently no cure, airway-clearance therapies, medications, nutritional support, and treatments targeting certain genetic variants have significantly improved health outcomes. 

 

The CDC’s Surveillance Study’s Caveat on Cystic Fibrosis and Mold

 

 

The CDC excluded 96 patients with cystic fibrosis (CF) from the study’s full case-classification process before arriving at the 968 potential cases analyzed. 

 

Since mold colonization is particularly common in respiratory specimens from people with CF, a positive lung culture may show that mold is present without establishing that it has invaded tissue or caused invasive disease. That makes these specimens harder to interpret using the same surveillance rules applied to patients without CF. 

 

 

Rather than categorizing these patients as confirmed cases, non-cases, or simple colonization, the surveillance team didn’t perform full medical-record abstractions or invasive mold disease classifications for them. Their specimens were instead archived for potential future study. As a result, this report can’t determine how many of the 96 patients had uncomplicated colonization, allergic or chronic fungal disease, or a true invasive infection. 

 

What is striking, however, is that mold colonization was considered common enough in people with cystic fibrosis that an entire group of patients had to be separated from the primary analysis. That should challenge the tendency to dismiss the presence of mold simply because it is expected or frequently encountered. While different than invasive mold disease, mold colonization poses significant health risks. Just because it’s so common in CF cases, this shouldn’t automatically be interpreted as clinically irrelevant.

 

This highlights the larger concern of whether we have become too comfortable normalizing fungal presence without asking how that presence can be contributing to illness.

 

Root-Cause Care for Mold Illness

 

 

When a fungal process is contributing to inflammation, relying only on anti-inflammatory corticosteroids can become fuel to the fire. 

 

Steroids may temporarily quiet inflammatory symptoms while simultaneously weakening the immune defenses responsible for recognizing, containing, and eliminating fungal organisms. Reducing inflammation isn’t the same as resolving why that inflammation is occurring.

 

Root-cause care asks what is driving the inflammatory fire in the first place. 

 

Is the patient reacting to an ongoing environmental exposure? Is the process allergic, inflammatory, colonizing, or truly invasive? Has immune dysregulation persisted after exposure, as described within the CIRS framework? Are damaged lung tissue, poor airway clearance, elevated blood sugar, medication use, or another illness making fungal control more difficult? 

 

This is important because invasive disease can require urgent antifungal treatment, while mold allergy, colonization, CIRS, and temporary exposure-related inflammation require different forms of evaluation and support. Treating every presentation the same risks both undertreating serious disease and overtreating findings that don’t represent invasive infection.

 

Molds and other fungi are natural parts of the environment and can’t be avoided completely. The goal is to limit unnecessary or excessive exposure while building greater resilience in the body’s terrain—the metabolic, immune, respiratory, tissue, and nervous-system conditions that influence how effectively the body responds when contact occurs. Healthy defenses should be able to recognize a threat, recruit the appropriate immune response, contain it, repair affected tissue, and then return to balance.

 

Root-cause care also means avoiding false either-or choices. Addressing the environment doesn’t replace medical evaluation, and antifungal treatment doesn’t automatically correct the conditions that allowed illness to develop. 

 

Likewise, nervous-system regulation can support recovery but should never be used to imply that a fungal infection, allergic response, or inflammatory illness is psychological. The most complete approach combines appropriate conventional treatment with an investigation of exposure, immune function, metabolic health, tissue integrity, medication risks, and persistent inflammatory signaling. 

 

Just because it’s common doesn’t mean it’s good. This reinforces why people with weakened immunity or impaired lung defenses must take mold exposure and their environments where they live and work seriously. 

 

Practical Ways to Reduce Mold Exposure

 

 

Removing or substantially reducing exposure is an essential first step across the spectrum of mold-related conditions. The treatment required after exposure is addressed will differ, but continued contact with a water-damaged environment can keep adding to the burden the body is attempting to manage. 

 

Because mold spores are naturally present indoors and outdoors, the goal is to correct abnormal moisture, remove contaminated materials, and reduce avoidable exposure. 

 

Prioritize Removal, Not Simply Killing Mold

Effective remediation should focus on correcting the source of moisture and physically removing mold and mold-damaged materials, rather than merely spraying, fogging, sealing, or attempting to kill the growth in place. 

 

Dead mold can still trigger allergic reactions, and contaminated material that is disturbed or broken apart may release smaller spores, particles, and fragments into the air. CIRS remediation efforts require additional steps, which you can find here.

 

The underlying water problem must also be corrected. Otherwise, mold can return even after visible growth has been cleaned. Leaks, flooding, condensation, poor drainage, plumbing failures, and excessive indoor humidity all need to be addressed as part of a complete remediation plan. Large, hidden, recurrent, or extensively contaminated areas may require an experienced professional who understands containment and can avoid spreading contamination into previously unaffected rooms.

 

Create the Safest Temporary Space Available

Not everyone can leave or remediate a home or workplace immediately. Until the larger problem can be resolved, identify the cleanest, driest room available and use it as a temporary safe haven for sleeping, resting, or working. 

 

A high-quality air purifier with appropriately sized HEPA filtration may help reduce airborne mold spores, particles, and fragments within that room. HEPA filtration can lower what is circulating through the air, but it can’t correct hidden growth, remove contaminated building materials, or make a room with active water damage truly safe.

 

Keep indoor relative humidity below 50%, using air conditioning or a dehumidifier when needed, and monitor it with an inexpensive hygrometer. Air filtration and humidity control are supportive measures—not substitutes for finding the moisture source and completing proper removal. The safest room shouldn’t contain active leaks, visible growth, persistent dampness, or a musty odor. 

 

Avoid or Limit Time in Water-Damaged Environments

Whenever possible, avoid buildings or rooms with active leaks, visible mold, persistent musty odors, flooding, or unresolved water damage. 

 

When entering an unknown or less-than-ideal environment can’t be avoided, limit the amount of time spent inside and consider appropriate personal protective equipment (PPE). An N95 may reduce inhalation exposure, but it doesn’t provide complete protection and shouldn’t be viewed as permission to remain in a heavily contaminated space longer than necessary. 

 

People who are immunocompromised, have chronic lung disease, or are at increased risk for invasive infection should speak with their trusted practitioner for protective recommendations and avoid mold cleanup whenever possible.

 

Reduce Exposure Without Living in Constant Alarm

Environmental awareness is important, but healing can’t revolve around fear, constant scanning, or the belief that every building and every symptom represents an immediate threat. Hypervigilance can keep the nervous system locked in a fight-or-flight response, worsening symptoms and the body’s overall capacity to recover. 

 

Practical precautions and nervous-system regulation should therefore happen together: take mold seriously, make informed environmental decisions, and also build tools that help the body recognize when it is safe enough to rest, repair, and return toward balance.

 

Pro-Tip: We created our Wholeness Method Mind-Body Program specifically to support people navigating CIRS and other complex mold-related conditions. The program helps individuals develop personalized tools for calming threat signaling, regulating the nervous system, responding to symptom flares, and supporting themselves through the uncertainty and stress that often accompany environmental illness. These practices don’t replace exposure removal or appropriate medical care, but they can become an important part of a more complete healing plan.

 

FAQs on the New CDC Mold Surveillance Study and Mold-Related Conditions

Here are our frequently asked questions regarding the new CDC mold surveillance study and mold-related conditions:[/vc_column_text]

Closing Thoughts on CDC’s Invasive Mold Surveillance Study

In our clinical practice, we’ve seen firsthand how devastating mold-related illness can be. We hope this new CDC surveillance study helps bring greater awareness to the seriousness and complexity of mold-related conditions, while encouraging more thoughtful conversations about exposure, susceptibility, diagnosis, and recovery.

 

Living with mold-related illness can feel overwhelming, particularly because mold is a natural part of our environment and complete avoidance is impossible.

 

But this information is meant to create clarity and empowerment. The more we understand how mold can affect the body, the better equipped we are to recognize potential problems earlier, reduce unnecessary exposure, ask better questions, and seek care that considers the full picture.

 

Knowledge can become an important part of healing. Even in complex cases, there are opportunities to improve the environment, strengthen the body’s resilience, regulate the nervous system, and address the underlying factors keeping someone stuck. Our hope is that greater awareness empowers more people to take an active role in their health and recognize that there may still be meaningful paths forward.

 

Work With Our Trusted CIRS Functional Medicine Practitioners

Our Empower Functional Health practice is honored to be trusted CIRS functional practitioners, supporting patients and clients from around the globe. We’re passionate about helping individuals achieve root-cause healing in order to live the life they are meant to, nearly symptom-free. We provide environmental illness thought leadership and evidence-based insights, paired with clinical pearls, to help you achieve your wellness goals. We welcome you to explore our free resources, and if you find that self-troubleshooting falls short, we’re here to guide you with personalized support and protocols. If you’re interested in working one-on-one with our CIRS functional team for your environmental illness healing journey, our CIRS Discovery Call is the best place to begin.

 

 

Disclaimer: We share this content to help you make informed and empowered decisions about your health. However, it is provided for educational purposes only and is not intended to diagnose, treat, cure, or prevent any condition or replace individualized medical advice. Always consult with a trusted qualified healthcare practitioner before beginning a new diet, supplement, treatment, or health protocol.