Multi-Center Molecular Diagnosis and Host Response of Respiratory Viral Infections in Pediatric Transplant Recipients

The participants are being asked to take part in this clinical trial, a type of research study, because the participants are scheduled to receive or have recently received a hematopoietic cell transplant (HCT) or a solid organ transplant (SOT). Primary Objective To determine if pre-transplant screening for respiratory viral load predicts RVI within 1- year post-transplant among survivors. Secondary Objectives: * To develop and validate a classifier based on pre-transplant immunological profile predictive of developing an acute respiratory viral infection (aRVI), with RSV/PIV3/HMPV/SARS-CoV-2 through one-year post-transplant among survivors. * To develop and validate a classifier based on Day +100 post-transplant immunological profiles predictive of developing an acute respiratory viral infection (aRVI),with RSV/PIV3/HMPV/SARS-CoV-2 through one-year post-transplant among survivors .

The investigators will collect a nasal swab and blood sample from the participant when the participant is enrolled on the study and if the participant develops a RVI in the first year after transplant. The investigators will collect a blood sample 100 days after the participant's transplant.