Co-infection with Influenza: Do Not Forget Aspergillus in the Immunosuppressed Neutropenic Host

To the editor: We read the comprehensive grand rounds review by Chertow and Memoli1 with great interest. The authors appropriately point out the frequent bacterial pulmonary co-infections following severe influenza. As immunosuppression is a well-known risk factor for complicating influenza2, we would like to point out the vulnerability of these patients not only to conventional bacterial super-infections (such as pneumonia due to Staphylococcus aureus, Pneumococcal pneumoniae, or gram negative rods), but also to opportunistic fungi, especially Aspergillus species. Although invasive pulmonary necrotizing aspergillosis has been described as a following influenza in apparently immunocompetent hosts3, single institution studies, encompassing the era before4 and during the H1N1 influenza pandemic5, mostly point out the occurrence of invasive aspergillosis in hospitalized patients with hematologic cancer. The frequency of this post-influenza complication is not well captured in the existing literature but its implications are twofold in immunocompromised patients. First, increased awareness needs to be made for prompt diagnostic work up and pre-emptive antifungal therapy targeting invasive molds in patients with complicated influenza course and suggestive radiologic findings (e.g., cavitary lesions, nodules, air-crescent sign). Second, although it has been limited in use by national health system6 and not been studied specifically, intensifying antifungal prophylaxis with the use of mold-active triazoles and increased surveillance by non-culture based diagnostic tests, such as Aspergillus galactomannan, might have an impact for post-influenza invasive aspergillosis, a disease with historically high mortality rates.