Molecular epidemiology and disease severity of influenza virus infection in patients with haematological disorders

nfluenza virus infection is a common cause of self‐limiting respiratory tract infection(RTI), however immunocompromised patients are at an increased risk for a severecourse of disease or fatal outcome. We therefore aimed to gain a betterunderstanding of the molecular epidemiology of influenza viruses from patientswith haematological disorders and their impact on the clinical course of disease.Molecular analysis using polymerase chain reaction (PCR) of nasopharyngeal swabswas performed for influenza virus in haematological patients at the HeidelbergUniversity Hospital. Clinical data was evaluated to identify associated risk factors.For phylogenetic analysis, the hemagglutinin (HA) gene was sequenced. Out of 159influenza positive patients, 117 patients developed upper RTI (influenza A:n= 73;influenza B:n= 44). Lower RTI was observed inn= 42 patients (26%),n= 22/42patients developed severe disease andn= 16/159 (10.1%) patients died. Risk factorsfor lower RTI were nosocomial infection (p= 0.02), viral shedding for≥14 days(p= 0.018), IgG levels <6 g/dL (p= 0.046), bacterial/fungal co‐infections (p< 0.001).Risk factors for fatal outcome were age≥65 years (p= 0.032), bacterial/fungal(p≤0.001) co‐infections and high viral load (p= 0.026). Sequencing of the HA gene(n= 115) revealed subtype A(H3N2) (n= 46), A(H1N1)pdm09 (n= 24), B/Victoria(n= 34), B/Yamagata (n= 11). There was no correlation between influenza (sub)typeand lower RTI. Influenza infection in haematological patients is associated withsignificant morbidity and mortality, the risk for aggravating co‐infections, prolongedviral shedding and nosocomial transmission emphasizing the need for infectioncontrol.Peer Reviewe