This study is for kids under 18 who are getting a bone marrow (hematopoietic cell) or organ transplant. Researchers want to see if checking for viruses before the transplant can predict if the child will get a respiratory (breathing-related) virus infection within a year after the transplant. They will take a nose swab and blood sample when you join the study and again 100 days after your transplant. This helps them understand how the body fights these infections.

• The study lasts for one year after the transplant, with sample collections at the start and 100 days post-transplant.
• Participants must be getting a transplant soon or have just had one, and must be under the care of a participating center.
• Parents/guardians must agree to the study, and if appropriate, the child must also agree.

There are no risks listed for the recipients, but donors must be ready to give a blood sample before the transplant. This study could help future transplant patients fight off viral infections better.