COVID-19 is now rapidly spreading worldwide.While the majority of COVID-19 patients show only mild or moderate symptoms,some could deteriorate quickly and may succumb to a sudden death.It is therefore important to identify who will be more likely to develop severe outcomes and be treated with particular or preventive care.Here in this literature survey,we collected epidemiologic and clinical data from 36 articles on 51,270 patients with different severity of COVID-19,aiming to characterize the population that are prone to severe condition and bad outcomes.These data reveal that old males and those with high BMI or underlying diseases,especially cardiovascular disease,hypertension and diabetes,are overrepresented among severe cases.High leukocyte and lymphopenia are common features in severe and critical patients.Upon deterioration of the disease,both CD4+and CD8+T cells are decreased,while almost all serum cytokines,especially pro-inflammatory cytokines,increased.