Respiratory syncytial virus in hematopoietic cell transplant recipients and patients with hematologic malignancies

Khawaja, Fareed; Chemaly, Roy F.

The proportion of RSV infections causing LRTI in HCT recipients ranges from 30% to 60% with higher rates reported in earlier years (in the early 1990s), 5, 21, 22 whereas in more recent studies, since year 2000, lower rates of LRTI (24-44%) have been observed. 4, 11, [23] [24] [25] 29, 30 This could possibly be explained by the increased use of ribavirin at earlier stages of RSV infection to prevent the infection from progressing to the lower respiratory tract, as well as the use of molecular assays for the detection not only of RSV but also other respiratory viruses. Recent studies from the Fred Hutchinson Cancer Research Center on respiratory viral infections in HCT patients applied specific definitions to better delineate the types of LRTI associated with respiratory viral infections. 31 Patients with proven or probable LRTI were defined as patients with microbiological detection of respiratory viruses in the lower respiratory tract with or without radiological evidence of disease in the lungs, respectively. Patients with possible LRTI were defined as patients with microbiological detection of respiratory viruses in the upper respiratory tract only and with radiological evidence of disease in the lungs. 31 In one of the studies, the proportions of patients with proven/probable or possible RSV LRTI were 48% and 52%, respectively. 31 Interestingly, the authors showed that patients with proven or probable LRTI had a higher need for supplemental oxygen use and for mechanical ventilation compared to those with possible LRTI. These definitions were also applied in studies on coronavirus, 32 parainfluenza virus 33 and rhinovirus. 34 Data on RSV infections in HM patients are scarce. Some studies have reported the rate of RSV infections in these patients. 4, 28, 29, [35] [36] [37] In an early study, the incidence of RSV was 31% among all symptomatic HM patients, including HCT recipients. A large proportion of these infections were diagnosed as LRTI (36%). 29 Similar studies reported a range of 3% to 37%, but the sample sizes were relative- ly small. 28, 35, 36 In a recent study, 181 HM patients with RSV infections were identified over 13 years. 37 Of these, 65% and 35% presented with URTI and LRTI, respectively. Among the HM patients with URTI, 13% progressed to develop a LRTI (73% were patients with leukemia, 27% with multiple myeloma, and none with lymphoma). 37 In a recent study from our institution focusing on RSV LRTI in HM patients who had or had not undergone HCT, we found that most HM patients who had not undergone HCT were defined as having possible RSV LRTI as bronchoscopy had not been performed in most of these patients at the time of diagnosis. 38 Few data are available with regards to RSV infections in pediatric HCT recipients. The estimated incidence of RSV infections among this population is 3% to 7%, 39, 40 with 22%-37% 39,41 developing LRTI.