A cluster of mucormycosis infections in hematology patients: challenges in investigation and control of invasive mold infections in high-risk patient populations

Mucormycosis has been reported to be occurring more frequently in hematopoietic stem cell transplant (HSCT) recipients in recent years. We investigated a hospital cluster of mucormycosis cases among patients with hematologic disorders. Case-patients were identified through hospital microbiology and pathology database searches and compared to randomly selected controls matched on underlying disease and hospital discharge date using conditional logistic regression. Environmental assessments, including collection of samples for fungal cultures, were performed. Of 11 case-patients, 6 (55%) had acute myelogenous leukemia and 3 (27%) were allogeneic HSCT recipients. Five case-patients (45%) died. In univariate analysis, case-patients were more likely than controls to have refractory hematologic disease (odds ratio [OR], 13.75; 95% confidence interval [CI], 1.31-689); neutropenia >14 days (OR, 11.50; 95% CI, 1.27-558) or to have received voriconazole prophylaxis (OR, 11.26; 95% CI, 1.11-infinity). A point source was not identified. Factors such as underlying disease state and antifungal prophylaxis type may identify hematology patients at highest risk for mucormycosis. Our investigation highlighted critical knowledge gaps, including strain typing methods, the role of the hospital environment in mucormycosis outbreaks, and hospital environmental infection control measures most likely to reduce exposure of immunosuppressed persons to mucormycetes.