Considering that EPO levels inversely correlate with the erythropoietic activity (Lezon C et al., 1995) and the short half-life time of EPO (less than 3 hours) these results suggest ongoing erythropoietic stress in mice with malaria, which is accordance with the parasitemia kinetics and the delayed reticulocytosis measured. The gene discussed is EPO; the disease is malaria.