A new study from the United States Centers for Disease Control and Prevention (CDC) suggests that invasive mould infections are a more significant and underrecognised health risk than previously assumed, particularly for people with weakened immune systems. While the research was conducted in Atlanta-area hospitals, its findings carry clear implications for European healthcare systems, where surveillance of such infections remains fragmented.
Published this week, the study aimed to quantify the incidence of invasive mould diseases — a group of rare but life-threatening infections caused by mould species that can invade and damage body tissues. Most infections occur through inhalation of spores, though the fungus can also enter via cuts, wounds, or contaminated medical equipment. For healthy individuals, these spores typically pose no problem, but for the elderly, cancer patients, and others with compromised immunity, they can be fatal. Treatment usually requires prolonged courses of antifungal drugs.
“It’s kind of the first time we’ve had an estimate like this,” said Jeremy Gold, the study’s senior author at the CDC. Understanding the scale of the problem is critical, he added, because the threat is likely to grow in the wake of natural disasters linked to climate change, such as hurricanes and floods. In Europe, similar concerns arise from rising water temperatures and extreme weather events that can facilitate mould proliferation.
No comprehensive European registry
At the European level, there is no comprehensive registry for invasive fungal infections. Unlike many other communicable diseases, these infections are not subject to EU-wide mandatory reporting. Surveillance instead relies on a patchwork of national programmes, leaving significant gaps in data. A 2024 study in The Lancet estimated a global burden of 6.5 million invasive fungal infections and 3.8 million deaths annually, but country-level figures for Europe remain uncertain.
The CDC team worked with four Atlanta-area hospitals and their affiliated outpatient clinics to identify potential cases between 2020 and 2024. They initially flagged nearly 1,000 potential cases but narrowed the number to about 450 after excluding patients who showed signs of exposure without meeting the criteria for invasive mould disease. The results showed that hospitals can expect to see three to five cases per year for every 100 inpatient beds, with higher rates at larger academic hospitals that treat more complex illnesses.
Most affected patients had impaired immune systems or were weakened by a prior COVID-19 infection. Gold noted that mould exposure can occur in hospitals or other healthcare facilities, but the study did not attempt to determine where each patient was first exposed. The data should give hospital administrators a benchmark for whether their own case numbers fall within the expected range or signal a possible outbreak.
Europe’s ageing population adds urgency to the issue. As the number of older people grows, so does the pool of individuals susceptible to these infections. In countries like Italy, Germany, and France, where the proportion of over-65s is among the highest in the world, healthcare systems may need to reassess their preparedness. The findings also echo concerns about industrial farming practices that can contribute to the spread of pathogens, though the link to mould requires further study.
The CDC study serves as a reminder that invasive mould infections are not just a problem for tropical or disaster-prone regions. With climate change driving more frequent floods and storms, and with medical advances enabling more people to survive with weakened immune systems, the risk is rising across the continent. European health authorities may need to consider establishing a coordinated surveillance system to track these infections and respond to outbreaks more effectively.
