ABSTRACT
COVID-19 is highly transmissible; however, its severity varies from one individual to another. Variability among different isolates of the virus and among its receptor (ACE2) may contribute to this severity, but comorbidity plays a major role on disease prognosis. Many comorbidities have been reported to be associated with severe COVID-19 patients. We have collected data from retrospective studies which include clinical and epidemiological features of patients and categorize them into severe/mild, ICU/non-ICU and survivors/dead patients. In this review, we give an update about SARS-CoV-2 structure with emphasis on the possible reasons for the severity of the virus in patients. We also collected information and patients' data to highlight the relation between COVID-19 patients and comorbidities.