Incidence of respiratory viral infections in adults following hematopoietic stem cell transplant (HSCT) at a tertiary care hospital in India.

Respiratory viral infections carry a major risk of mortality and morbidity for HSCT recipients. It is important to analyze their seasonality, incidence, disease burden and associated risks. Hundred HSCT recipients were followed up prospectively for acute respiratory infection episodes for 18 months. qRT-PCR was performed for influenza virus (influenza A and B), human metapneumovirus (HMPV), respiratory syncytial virus (RSV), adenovirus, rhinovirus and parainfluenza virus (PIV 1-4). A total 318 respiratory episodes occurred, of which 252 episodes were seen in autologous (n = 78) and 66 episodes in allogeneic HSCT (n = 22). Of the total 158 episodes for which samples could be collected, 61(38.6%) tested positive. A higher infection rate (42.2%) was seen in autologous compared with allogeneic HSCT (25.7%). The most common viruses detected were rhinoviruses (31.1%), followed by PIV (19.6%), hMPV (16.3%), RSV (18%) and influenza viruses (14.7%). There were 5 episodes with the involvement of more than one virus and there were 94 episodes of lower respiratory tract infection (LRTI). The commonest viruses detected in LRTI were rhinovirus (18.6 per 100 patient years), followed by PIV (11), RSV (10), hMPV (8.9) and influenza virus (7.9). The in-hospital case fatality ratio was 30% for hMPV and 11.1% for influenza A/H3N2 virus. Respiratory viral infections are common in HSCT recipients. Higher mortality was seen in allogeneic recipients. Rhinoviruses are an important cause of infections in these groups. Immunizations for vaccine preventable viruses like influenza and RSV which shows high incidence needs to be considered.