Anthony Denatala, CMRS · July 30, 2026 · 5 min read
A new CDC surveillance study published this week in the agency's Morbidity and Mortality Weekly Report found that invasive mold disease hospitalizations are likely far more common than previously understood — and that when people do get sick, roughly one in three die before leaving the hospital.
Researchers at the CDC's Georgia Emerging Infections Program spent five years — 2020 through 2024 — tracking mold-related illness across four Atlanta-area hospitals and their affiliated clinics. They started with nearly 1,000 potential cases and confirmed 449 that met the definition for invasive mold disease. About a third of those patients died during their hospitalization.
The study's senior author, CDC physician Dr. Jeremy Gold, described it as a first-of-its-kind estimate: "It's kind of the first time we've had an estimate like this." That's because the government has never required doctors to report these cases. There is no national registry. No mandatory tracking. The actual scale of mold-related illness in the United States has never been precisely measured — and according to this research, it is almost certainly larger than current estimates suggest.
The CDC had previously estimated more than 15,000 hospitalizations per year nationally could be tied to invasive mold disease. This new research provides a local-level benchmark for the first time: hospitals should expect between 3 and 5 inpatient cases per year for every 100 inpatient beds. At academic medical centers — the larger hospitals that handle more complex cases — that figure climbs to nearly 5 inpatient cases per 100 beds and 14 ICU cases per 100 ICU beds.
These are not small numbers for a condition that is classified as rare. And because there is no reporting requirement, the CDC is working off surveillance data from four hospitals. Extrapolating to thousands of hospitals across the country with widely varying environments, patient populations, and building conditions means the true national burden is almost certainly higher.
Key Findings From the CDC Study
Most of the patients in this study had compromised immune systems — cancer treatment, organ transplants, or COVID-19 infection had left them unable to fight off mold spores the way a healthy person's body would. The elderly were also disproportionately represented. These are the groups we have always been trained to identify as high risk in environmental consulting work.
But the finding that stands out most in the full study data: 35% of confirmed cases had no classic immune risk factors. More than one in three patients who developed serious invasive mold disease did not fit the standard high-risk profile. The CDC specifically flagged this — noting that clinicians and surveillance programs need to consider the possibility of mold disease even in patients who don't present with obvious immunosuppression.
That matters for residential mold work. The conventional framing is that mold is a problem mainly for people who are already sick. This study suggests otherwise. A significant portion of people who developed life-threatening mold infections were not in a recognized high-risk category before they got sick.
The study period — 2020 through 2024 — overlaps with the COVID-19 pandemic, and the data reflects it. Thirteen percent of the confirmed mold disease cases had a current or recent COVID-19 diagnosis. Prior research from the same Atlanta surveillance program found that patients with active COVID and a simultaneous fungal infection had a 75% in-hospital mortality rate, compared to 27% for patients with fungal infection alone.
COVID disrupts the lung's physical barriers. When that happens, mold spores that would normally be cleared by the immune system have a pathway to establish an infection. The COVID-associated mold disease peak was in 2021 at 23% of cases, and it dropped to 5% by 2024 — but the mechanism remains relevant for anyone whose respiratory system has been compromised, for any reason.
Invasive mold disease is not a nationally notifiable condition. Physicians are not required to report it. There is no federal tracking system. The CDC is essentially running surveillance at a handful of hospitals and using that data to estimate what is happening everywhere else.
What this means in practice: when someone gets sick from mold exposure in their home, there is no mechanism that connects that illness back to the building where they were exposed. The environmental piece — where the spores came from, what conditions allowed them to grow and concentrate — is almost never investigated as part of the clinical workup. The hospital treats the infection. The house stays the way it is.
I have been in buildings where the mold load was significant enough that I could measure it in real time. I have written inspection reports documenting conditions that, for the right person at the right moment of vulnerability, represent a genuine health risk. The CDC study is a clinical confirmation of what those of us doing environmental work have observed for years: the problem is larger than the official numbers suggest, and the people most at risk are often the people least able to recognize what they are being exposed to.
The CDC study focused on invasive disease — the kind that requires hospitalization. That is not the same as the chronic low-level exposure that drives most of the calls I receive. But the study is a useful reminder that mold is not purely a cosmetic issue, and that for certain people in certain conditions, the stakes are higher than most homeowners are led to believe.
If someone in your household has a compromised immune system, is recovering from a respiratory illness, is receiving cancer treatment, is elderly, or is an infant, a known mold problem in the home is not something to defer. The window between exposure and serious illness is shorter for those populations than most people realize.
The first step is always a proper inspection — not a visual guess, not a home test kit, but a thorough walkthrough with moisture mapping, physical sampling, and written findings. If there is a problem, it needs to be scoped accurately. If there is not, that documentation is worth something too.
Have questions about mold in your home?
Anthony Denatala, CMRS — 20+ years in environmental consulting. Forensic inspection, air sampling, written protocol. Same-week availability.
Source: CDC MMWR Surveillance Summary — Active Surveillance for Invasive Mold Disease, Four Hospitals, Atlanta, Georgia, 2020–2024. Published July 28, 2026. Authors: Sajewski ET, Mackey C, Thomas S, et al.
