A photo taken from the peripheral blood smear of an MDS patient (undergoing chemotherapy) with H1N1 influenza infection, showing 4 immunoblasts. Immunoblasts can be seen in infection, such as Infectious Mononucleosis, and are a prominent finding in Hantavirus infection. In this patient they comprised 20-25% of the WBCs and were concentrated in and near the feathered edge. There was rouleaux formation and relative eosinophilia, but the overall WBC was low (600 cells per microliter).