Hidden Mould in the Air: A Practical Narrative Mini-Review of Invasive Mould Infection Prevention for High-Risk Patients and Clinicians.

Airborne mould spores, including those of the Aspergillus species, are ubiquitous both indoors and outdoors. While they are generally harmless, inhaled spores can cause severe infections, particularly invasive pulmonary aspergillosis, in patients with impaired immune defences. Allergic manifestations such as asthma arise by different mechanisms and are not covered. This narrative mini-review summarises key evidence and guideline recommendations for healthcare teams and provides practical, patient-friendly advice by highlighting clinical and infection-prevention considerations. As there is no safe exposure threshold or minimum infectious dose for individual patients, prevention focuses on reducing avoidable exposure during high-risk periods. These high-risk periods typically refer to medical conditions such as prolonged neutropenia, the early post-transplant period, and high-dose corticosteroid therapy. Furthermore, prevention also focuses on optimising hospital environmental controls by implementing high-efficiency particulate air filter filtration, protective rooms and construction dust containment, alongside antifungal prophylaxis when indicated. The most impactful measures at home are preventing and rapidly remediating visible mould and dampness, avoiding high-spore activities such as composting, handling potting soil, and working with demolition or renovation dust, and maintaining simple hygiene practices that reduce dust reservoirs. This narrative mini-review also summarises what the literature can and cannot provide. Although Aspergillus species account for most of the available evidence, the same exposure-reduction principles apply to other environmentally acquired moulds, including Mucorales, Fusarium species and Scedosporium species.