Community acquired respiratory viruses (CARV) are an important cause of morbidity and mortality among Hematopoietic Stem Cell Transplant recipients (HSCT). Reported incidence of CARV in HSCT varies from 4% on early days of antigen testing to ∼40% using PCR based detection. Most commonly detected viruses are Rhinovirus/enterovirus (22-34%), followed by Influenza, Respiratory Syncytial Virus (RSV) and Parainfluenza on similar range. Less frequently, with important morbidity associated are Coronavirus (3-11%), Adenovirus and Human metapneumovirus (HMPV).
Influenza pneumonia have attributable mortality in HSCT ∼ 12%. Progression to lower respiratory tract infection (LRTI) can occur in one third of patients. However, perceived less aggressive viruses can progress to LRTI with equally precarious outcomes. For example, RSV have attributable mortality ∼ 15%, with some series describing mortality around 80% in untreated patients. Adenovirus disseminated infection has been reported around 50% in small series, with mortality ranging 23%. Associated risk factors for LRTI progression include age greater than 65, lymphopenia, neutropenia, unrelated donor and chronic graft versus host disease.
Bacterial coinfection, bronchiolitis obliterans and decline in pulmonary function are complications frequently described after CARV infections. Allograft related shortcomings remained an important area of research.
General preventive measures are recommended to reduce infection related complications. Great example is Influenza vaccination and antiviral prophylaxis in specific scenarios. Immunization for several other CARV remains in development and not commercially available. Impact of contact and respiratory precaution at level of health care has been documented in several studies and should be followed. Other interventions like palivizumab for RSV in adults still lacking enough data and difficult implementation due to cost.
Therapeutic options are narrow given limited antiviral agents approved for the wide range of CARV. Influenza therapy is known to improve outcomes. Ribavirin (RBV) with or without IVIG has reported to beneficial for RSV, PIV and anecdotic reports for HMPV. RBV IV or inhaled (teratogenic and only FDA approved) administration poses a logistic challenge and associated to several side effects. Cidofovir for Adenovirus, ALN-RSV01 (RSV), DAS-181 (PIV), specific T-cell immunity therapies, among others, should accumulate more data to be suited for general use.