Clinical characteristics and outcomes of viral respiratory infections in allogeneic haematopoietic stem cell transplantation recipients: a single-centre experience

<b>Introduction.</b> Allogeneic haematopoietic stem cell transplantation (allo-HSCT) is a treatment option for haematological malignancies. Allo-HSCT patients are more susceptible to viral infections due to immunosuppression.<b>Gap Statement.</b> The bone marrow transplant programme in Qatar, established within the past decade, remains in a developmental phase. A thorough evaluation of infection-related outcomes is essential to identify areas for improvement and to enhance infection control measures.<b>Aim.</b> This study aims to estimate the incidence, clinical impact and outcomes of viral respiratory tract infection (vRTI) in allo-HSCT recipients.<b>Methodology.</b> A total of 64 allo-HSCT patients were included in this study. Respiratory samples were collected from patients presenting with respiratory symptoms or during episodes of febrile neutropenia without an identified source. Nasopharyngeal swabs were the primary sampling method for upper respiratory tract infections (URTIs), while sputum, bronchoalveolar lavage or tracheal aspirates were obtained in patients with lower respiratory tract involvement or those requiring mechanical ventilation. During the high-risk COVID-19 pandemic period, pre-admission screening for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was routinely performed for all patients undergoing transplantation or chemotherapy. All samples were assessed using multiplex PCR assays. Viral agents, outcomes of vRTI occurring in the period of 1 year after allo-HSCT, clinical symptoms, infection-related complications and risk factors were reviewed.<b>Result.</b> A total of 64 allo-HSCT patients were reviewed; 41 of them (53%) had vRTI. SARS-CoV-2, respiratory syncytial virus (RSV), rhinovirus, influenza and parainfluenza were the most common viruses. Importantly, 19 patients (46.3%) had URTI, and 22 patients (53.7%) progressed to pneumonia. The risk of vRTI was significantly related to non-corticosteroid immune suppressants (<i>P</i>≤0.01) and to lymphopenia (<i>P</i>≤0.05). RSV (66.7%), coronaviruses (229E, NL63, OC43 and HKU1) (60%) and rhinovirus (58.3%) were the most dominant viruses associated with the development of pneumonia. Thirteen patients (20.3%) were admitted to the ICU; eight of them were associated with vRTI (61.5%). Ten deaths were reported (15.6%); vRTI was the primary cause of death in one of the deceased patients.<b>Conclusion.</b> Early detection and intervention strategies are crucial in mitigating the impact of these infections. The immune alteration effect of prophylaxis immune suppressants and antiviral therapy exacerbates the risk of infections among allo-HSCT patients. Novel antiviral approaches based on enhancing antiviral immune responses, vaccines and non-pharmaceutical preventive strategies are required to improve outcomes in allo-HSCT patients.