CD4 and macrophage activation syndrome: In the late stage of COVID-19, the symptoms of the disease manifests including Macrophage Activation Syndrome (MAS) and secondary Hemophagocytic Lymphohistiocytosis (HLH) as well as a poor number of several types of lymphocytes including CD4+, CD19+ and NK lymphocytes with cytokine storm containing IL-1, IL-6 and IL-10 (48, 76).