Community Airborne Mold Spore Counts and Invasive Fungal Disease Risk Among Pediatric Hematological Malignancy and Stem Cell Transplant Patients

Background Patients with hematological malignancies and hematopoietic stem cell transplantation (HSCT) recipients are at risk of developing invasive fungal infections, but the quantitative risk posed by exposure to airborne mold spores in the community has not been well characterized. Methods A single-institution, retrospective cohort study was conducted of pediatric patients treated for hematological malignancies and HSCT recipients between 2014 and 2018. Patients with invasive fungal disease (IFD) due to molds or endemic fungi were identified using published case definitions. Daily airborne mold spore counts were obtained from a local National Allergy Bureau monitoring station and tested for association with IFD cases by zero-inflated Poisson regression. Patients residing outside the region or with symptom onset more than two weeks after admission were excluded from the primary analysis. Results Sixty cases of proven or probable IFD were identified of which 47 cases had symptom onset within 2 weeks of admission and were therefore classified as possible ambulatory onset. The incidence of ambulatory-onset IFD was 1.2 cases per 10,000 patient-days (95% CI, 0.9-1.7). A small excess of ambulatory-onset IFD was seen from July through September during which period spore counts were highest, but this seasonal pattern did not reach statistical significance (P = 0.09). No significant association was found between IFD cases and community mold spore counts over intervals from one to six weeks prior to symptom onset. Conclusions There was no significant association between IFD cases and community airborne mold spore counts among pediatric hematological malignancy and HSCT patients in this region.