A retrospective Belgian study of influenza patients admitted to ICU between September 2009 and March 2011 showed that 9 of 40 (23%) patients had IAPA. Four cases (44%) were proven despite not being immunocompromised according to the EORTC/MSGERC consensus definitions [7]. The median time between influenza diagnosis and IAPA was 2 days (range 0–4 days). All IAPA patients had positive BAL GM, and 78% had positive serum GM, despite not being neutropenic. Eighty-nine percent of patients had Aspergillus growth in BAL culture (almost exclusively Aspergillus fumigatus), and 55% of patients had endobronchial lesions observed during bronchoscopy, possibly indicating invasive tracheobronchitis [7]. Similar performance characteristics of BAL GM and culture were reported in two other cohort studies [8, 9]. BAL sampling is thus an important diagnostic procedure as serum GM can be negative and sputum/tracheal aspirate cultures can remain sterile.