The aim of this study is to determine the frequency and causative virus of viral infections seen after hematopoietic stem cell transplantation (HSCT) in pedaitric patients, the effect of the immunosuppresive agents and antiviral prophylaxis to viral infections, to evaluate the efficacy of antiviral treatment used for viral infections, the impact of viral infections on mortality after HSCT.

295 pediatric HSCT patients between April 2010-August 2022 from a Children's Stem Cell Transplantation Unit were included. Patients’ demographic info, HSCT-related data, GVHD prophylaxis regime, antiviral prophylaxis after HSCT, the time span of prophylaxes applied, 27 different viral infections diagnosed from serum, stool and nasopharyngeal swab samples after HSCT, their frequencies and their timespans, patients’ mortalities were documented from patients' files.

68% of 295 patients were documented with a viral infection, most common isolates are CMV 26%, EBV 11%, ADV 9%, COVID-19 9%, BKV 7%, VZV 6%. Mortality rates are CMV 27%, EBV 38%, ADV 47%. Virus detection after HSCT is 1,10 months for CMV, 2,33 for EBV, 1,16 for ADV, 11 for VZV, 1 for BKV. The most common co-infections documented are CMV/EBV. For CMV treatment 69% valgancyclovir, 54% gancyclovir, 7% foscarnet is used. 53% of VZV infections were seen after acyclovir prophylaxis is stopped.

HSCT is a curative treatment for a variety of hematological diseases, immune deficiencies, solid organ tumors, some genetic and metabolic disorders. With preparations before HSCT and the GVHD prophylaxis after HSCT, patients become immunosuppressive and susceptible to opportunistic viral infections. Viral infections have an impact on mortality, and it is beneficial to know the common viral agents, when they are detected, viruses that are frequently detected together, and their treatment responses.