The Clinical Impact of Infection with Swine Flu (H1N109) Strain of Influenza Virus in Hematopoietic Stem Cell Transplant Recipients

There are limited data on the impact of H1N109 infection in patients undergoing hematopoietic stem cell transplantation (HSCT). We reviewed individual medical records of patients who underwent HSCT or were on follow-up post-HSCT between May and September 2009. Thirteen patients with H1N109 infection were identified: 2 <100 days post-HSCT, 7 >100 days post-HSCT, and 4 just prior to HSCT. Five (38.7%) had lower respiratory tract involvement (LRTI), whereas the remainder had upper respiratory tract involvement (URTI). LRTI occurred in patients who were profoundly neutropenic post-HSCT or on potent immunosuppression for chronic graft-versus-host disease (cGVHD). At 100 days post-H1N109 infection, only 1 patient with LRTI survived, whereas all with URTI are alive. Four patients successfully treated for H1N109 infection prior to HSCT underwent the procedure after 4 to 6 weeks without any complications. Another 6 patients received oseltamivir prophylaxis during conditioning and none developed H1N109 infection. In conclusion, H1N109 infection was associated with LRTI in HSCT recipients who were profoundly neutropenic or immunosuppressed. Prior H1N109 infection did not affect the successful outcome of HSCT and oseltamivir prophylaxis in a small group of recipients resulted in no infection. Further studies are required.