The expression of CD35 antigen on the surface of RBCs was assessed by flow cytometry. Compared to CD35 expression from the controls, no obvious differences were observed from the healthy people(around 4.69) (Fig 2-1). In the positive samples, the CD35 values increase from the negative 4.69 to 10.61 (Fig 2--2). In the outbreak cases, however, a sharp increase of CD35 antigen expression at the RBC external membrane were observed with the values of 28.76(Fig. 2–3 and 2–4), which were significantly higher than the value of the control samples (p<0.01). The long-term infectious of eperythroon would cause a sharp decrease of the CD35 levels from 28.76 to 2.31 (Fig. 2–5) (p<0.01), which is even much lower than that of the health people (4.61).