[Respiratory virus infections after hematopoietic cell transplantation]

Respiratory viral infection is a common disease even among immunocompetent individuals. Moreover, approximately 40% of the hematopoietic cell transplantation (HCT) recipients suffer from a respiratory infection within 100 days after HCT. New respiratory viruses have been continuously identified in the past 20 years, such as new strains of coronaviruses (CoV), human metapneumovirus (HMPV), and human bocavirus (BoV). In 2019, severe acute respiratory syndrome coronavirus (SARS-CoV)-2 that caused the coronavirus disease (COVID)-19 pandemic was identified. The 30-day overall survival after lower respiratory tract disease (LRTD) due to CoV, including SARS-CoV-2 or HMPV, was 60-70%, which is similar to that after LRTD due to influenza or respiratory syncytial virus. However, whether BoV is a pathogen of LRTD remains unclear. Moreover, corticosteroid has been reported as an efficient drug for LRTD due to SARS-CoV-2. Antiviral drug (remdesivir), anti-IL-6 receptor antibody (tocilizumab), and JAK inhibitor (ruxolitinib) are also expected to be efficient for the treatment of COVID-19. Thus, managing respiratory viruses in HCT recipients needs to be learned based on experiences from the COVID-19 pandemic.