The Geneva Blood Virome Project is a longitudinal observational study. The main objective is to describe the kinetics of the plasmatic viral load of a selection of at least 21 DNA and RNA viruses of the blood virome in allogeneic hematopoietic stem cell transplant recipients, over a one-year period after transplantation. Secondary objectives are: 1) to assess the prevalence of DNA and RNA viruses plasmatic detections and co-detections, 2) to assess the cumulative incidence of DNA and RNA viruses plasmatic detection. The population of the study consists in adult patients receiving allogeneic stem cell transplantation at the University Hospitals of Geneva, enrolled in an already existing monocentric cohort, and for which clinical specimens are collected and stored at the time and after transplantation. The investigators plan to include 120 patients whose plasma samples are collected from March 2017 and to systematically use plasma samples collected on the day of transplantation and several time points after transplantation to screen DNA and RNA viruses by qualitative and quantitative real-time PCR and RT-PCR.

The Geneva Blood Virome Project is a longitudinal observational study. The main objective is to describe the kinetics of the plasmatic viral load of a selection of at least 21 DNA and RNA viruses of the blood virome (Herpesviridae Polyomaviridae, Adenoviridae, Parvoviridae, Anelloviridae, Picornaviridae and Flaviviridae) in allogeneic hematopoietic stem cell transplant recipients, over a period of one year after transplantation. These DNA and RNA viruses can be responsible of acute infections, chronic infections or reactivations after transplantation. Secondary objectives are : 1) to assess the prevalence of DNA and RNA viruses plasmatic detections and co-detections at pre-specified time-points, 2) to assess the cumulative incidence of DNA and RNA viruses plasmatic detection at pre-specified time-points. The population of the study consists in adult patients receiving allogeneic stem cell transplantation at the University Hospitals of Geneva and who are enrolled in an already existing monocentric cohort named "Cohort of infectious disease in hematopoietic stem cell transplant patients" and for which clinical specimens are collected and stored at the time and after transplantation. The investigators plan to include 120 patients whose plasma samples are collected from March 2017 and to systematically use plasma samples collected at 5 pre-specified time points (the day of transplantation, 30 days, 3 months, 6 months, and one year after transplantation) to perform qualitative and quantitative real-time r(RT)-PCR assays for the screening of DNA and RNA viruses. The definitive analysis of results should be done by the end of 2020.

Inclusion Criteria:

• Adult patients receiving allogeneic stem cell transplantation since March 2017 at University Hospitals of Geneva
• Enrollment in the "Cohort of infectious disease in hematopoietic stem cell transplant patients"
• Signature of an informed consent form before transplantation

Exclusion Criteria:

• Absence of a signed informed consent form for the "Cohort of infectious disease in hematopoietic stem cell transplant patients".

Adult patients receiving allogeneic stem cell transplantation at University Hospitals of Geneva and who are enrolled in an already existing monocentric cohort named "Cohort of infectious disease in hematopoietic stem cell transplant patients"