Background: In 2011, the ECIL-4 conference prepared three sets of guidelines on prevention, diagnosis and treatment of community-acquired respiratory viruses (CARVs) such as Human Influenzavirus (IV-A/B), Human Respiratory Syncytial Virus (HRSV), Metapneumovirus (HMPV), Parainfluenzavirus (HPIV), Rhinovirus/Enterovirus (HRhV/ EV), Coronavirus (HCoV) and Adenovirus (HAdV). Purpose: To provide one single comprehensive update on management of CARVs in patients with HM, auto-HCT, and allo-HCT. Method: Experts from Europe and the USA reviewed the CARV literature since 2011 and prepared updates as of September 2019. The group suggested changes to previous recommendations using the ECIL grading and presented these to the delegates of ECIL-8 (http://www.ecil-leukemia. com/program2019.htm), who suggested revisions, and approved the finalized slide set (http://www.ecil-leukemia. com/resources.htm). Results: In general, most data were available for adult allo-HCT patients, but only limited evidence for children, for auto-HCT, and HM patients. The need for harmonized clinical case definitions was approached by working definitions covering upper and lower respiratory tract infectious disease (RTID), and specifically CARV pneumonia. Nucleic acid testing (NAT) detecting CARV genomes in respiratory specimens are recommended for a laboratory-confirmed diagnosis of RTI (AII), and rapid tests preferred for decisions regarding infection control, antiviral and/or antibiotic treatment, and deferral considerations regarding chemotherapy or HCT (BIIt). Detailed tables provide infection control and deferral recommendations for specific CARVs and patients at risk. IV-A/B vaccination is recommended, whereby quadrivalent vaccines are preferred if available (BIII). Neuraminidase inhibitors (NAI) for routine seasonal prophylaxis was discouraged (BIII), but post-exposure prophylaxis using treatment dose was recommended (AIIt). Insufficient evidence limits recommendations regarding NAI double-dose, prolonged administration or use of baloxavir. RSV prophylaxis with palivizumab for seasonal or post-exposure prophylaxis in children >2 yrs or severely immunocompromised patients is limited by insufficient evidence and high costs (CIII). Allo- HCT patients at high risk of progression to, or with diagnosis of RSV-lower-RTID should be treated with systemic or aerosolized ribavirin (BII). HMPV and HPIV treatment recommendations are limited by evidence, but some centers consider systemic ribavirin in allo-HCT patients at high risk (CIII). Adjunct use of intravenous immunoglobulins (IVIg) for HRSV, HMPV, and HPIV was judged as insufficient even in patients with hypogammaglobulinemia of <4.5 g/L. Corticosteroid use of >1 mg/kg/day has been associated with poor course, and reduction to <1 mg/kg bw/day could be considered (CIII). Insufficient data exist for treatment recommendations of HCoV and HRhV/EV RTID. If HAdV is detected in blood >1000 c/mL in ymphopenic patients (<100 cells/uL) with upper RTID or with HAdV LRTID/pneumonia, intravenous cidofovir may be considered (5 mg/kg bw once weekly; together with probenecid, hyper-hydration, and monitoring of renal function) (BII). No recommendations regarding brincidofovir for HAdV could be given. Conclusions: Despite significant progress in adult allo- HCT, the working group identified significant gaps in knowledge and treatment of CARVs. Most data are available for IV-A/B and HRSV, less for HMPV, HPIV, HCoV, HRhV/EV, and HAdV. Prospective multicenter cohort studies determining the risk factors of progression to LRTID and -attributable mortality, validation of risk scores for progression to LRTID, morbidity, mortality, and more efficacious prevention and treatment options are urgently needed including novel antivirals, monoclonal antibodies, and vaccines.