Erythema Infectiosum (Fifth disease)
Invades and destroys red blood cell precursors and halts the red cell production
EBV
Strep infection
Use of hydroxyurea
Invades and destroys red blood cell precursors and halts the red cell production
Aplastic crisis
Tumor lysis syndrome
Sickle cell crisis
Immune reconstitution syndrome
Acute transfusion reaction
Leukemia 
Leukemia
Acute myeloid leukemia