Project SummaryInvasive infections by Aspergillus fumigatus and other Aspergillus species are leading causes of mortality andmorbidity among profoundly immunosuppressed hosts. Recently, invasive aspergillosis has been described asa complication of severe influenza infection, predominantly among patients who lack traditional aspergillosis riskfactors. Despite an increasing number of case reports of influenza-associated aspergillosis (IAA), the incidenceand clinical features of the disease in the United States (US) are unknown. Whereas risk factors for aspergillosisare well described in immunosuppressed populations, they have not been defined for patients with severeinfluenza. In the largest studies of IAA to date, investigators retrospectively diagnosed the disease in 14%-19%of intensive care unit (ICU) patients with influenza at 7 European hospitals from 2009-16; the mortality rate ofIAA was 50%. Comparable incidence has been described in retrospective reports from single ICUs, but rates ofAspergillus superinfections in most multi-center studies of severe influenza have been lower. In the absence ofsystematic testing for aspergillosis among patients with severe influenza, it is possible that IAA is under-recognized by US clinicians and under-reported in the literature. At the same time, incidence may be overstatedin the retrospective European studies by liberal acceptance of serum or bronchoalveolar lavage fluid (BALf)galactomannan as definitive markers of disease. Our objectives in this project are to define the incidence, clinicalcharacteristics, and risk factors of IAA by conducting the first prospective study of the disease in the US. We willemploy strict IAA case definitions and systematic serum and BALf galactomannan diagnostic testing of ICUpatients with severe influenza. We hypothesize that we will demonstrate rates of IAA in the US that arecomparable to those reported in Europe, and that a novel point-of-care galactomannan lateral flow assay (LFA)will demonstrate strong sensitivity and specificity for diagnosing IAA. In aim 1, we will conduct a prospective,observational clinical study of IAA in ICUs at 4 large medical centers from different regions of the US. In aim 2,we will evaluate the performance of serum and BALf galactomannan LFA for diagnosing IAA. Our findings willallow us to develop strategies for rapidly and accurately identifying patients with IAA. This study addressesfundamental gaps in understanding of the epidemiology and clinical aspects of an under-appreciated form ofinvasive aspergillosis. It will lead to clinical trials in which improved understanding of IAA and its diagnosis areused to guide early antifungal treatment strategies, as well as to future laboratory studies of IAA pathogenesis.The project is feasible due to the multidisciplinary expertise of our collaborative team of pre-eminent physician-investigators. Finally, the study has the support of the US Centers for Disease Control and Prevention and arecently-formed international IAA consortium, relationships that will useful in designing and executing follow-upprojects.