Invasive mould infections are more common than thought, study finds

Published on 30/07/2026 - 14:56 GMT+2 Invasive mould infections may be an underrated and potentially deadly threat for those with weakened immune systems, according to a new study. ADVERTISEMENT ADVERTISEMENT The findings, published this week by the United States Centers for Disease Control and Prevention (CDC), aimed to better understand how common illnesses caused by mould – known as invasive mould diseases – are. “It's kind of the first time we've had an estimate like this," said the CDC's Jeremy Gold, the study's senior author. Understanding the scale of the problem is critical, he added, as it is likely to grow in the wake of natural disasters linked to climate change, such as hurricanes and floods. There are currently no aggregated global estimates of fungal disease incidence and mortality. A 2024 Lancet study estimated a global burden of 6.5 million invasive fungal infections and 3.8 million deaths annually. At the European level, there is also no comprehensive registry — invasive fungal infections are not subject to EU-wide mandatory reporting, and surveillance instead relies on a patchwork of national programmes. Meanwhile, there’s a growing population of older people who are more susceptible to such illnesses, Gold added. Invasive mould diseases are a diverse group of rare, life-threatening infections caused by certain mould species that can invade and damage body tissues. Most infections occur by inhaling mould spores, though the fungus can also enter the body through cuts, wounds, or contaminated medical equipment. For most people, the spores cause no health problems, but they can be life-threatening for the elderly, cancer patients, and others with weakened immune systems. Treatment generally requires prolonged courses of antifungal drugs. What the data showed To better understand how common such cases are at a local level, the research team worked with four Atlanta-area hospitals and their affiliated outpatient clinics to identify potential cases between 2020 and 2024. They initially identified nearly 1,000 potential cases, but narrowed the number down to about 450 by ruling out patients who showed signs of exposure but did not meet the criteria for invasive mould disease. The team found that hospitals can expect to see three to five cases per year for every 100 inpatient beds, with higher rates at larger academic hospitals, which tend to see more complex illnesses. Most affected patients had impaired immune systems or — in several cases — were weakened by a prior COVID-19 infection. Mould exposure can occur in hospitals or other healthcare facilities, but the study did not attempt to determine where each patient was first exposed, Gold said. He added that the data should give hospital administrators a benchmark for whether their own case numbers fall within the expected range, or signal a possible outbreak.