Introduction
Invasive pulmonary aspergillosis (IPA) is a well-recognized disease affecting immunocompromised individuals with prolonged neutropenia, inherited neutrophil disorders or T cell defects, with the risk depending on the patients’ underlying disease and the type and duration of immunosuppressive therapy [1]. Patients at the highest risk of invasive aspergillosis (IA) include those undergoing intensive chemotherapy for acute leukemia (AL) or recipients of allogeneic cell transplantation (alloHCT) who develop severe graft-versus-host disease, for whom antifungal prophylaxis is currently recommended [2, 3]. With changing treatment modalities, new risk groups continue to emerge, such as patients treated with ibrutinib [4, 5].
Although over the past four decades a link between influenza and IPA has been noted in single cases [6], recent cohort studies provide new insights into the epidemiology and clinical presentation of IPA in intensive care unit (ICU) patients with influenza [7–9]. Patients presenting with influenza-associated pulmonary aspergillosis (IAPA) may have classic European Organization for Research and Treatment of Cancer (EORTC)/Mycosis Study Group Education and Research Consortium (MSGERC)-defined host factors [10], but a notable proportion of patients was deemed to be at low risk of IPA, including previously healthy individuals. In addition, the clinical and radiological presentation was often atypical with radiological features that were not considered suggestive of invasive fungal disease. As a consequence, we cannot classify these patients according to existing consensus definitions, i.e., the EORTC/MSGERC definitions and the AspICU algorithm for classification of IPA patients in the ICU [10, 11]. We therefore set out to discuss current insights into the epidemiology, pathogenesis, diagnosis and management of IAPA and to propose case definitions that can facilitate homogeneity and comparability in clinical studies.