As the Corona Virus Disease 2019 (COVID-19) continues to spread globally, it is necessary to systematically understand the characteristics of the disease and cases. The purpose of this meta-analysis was to evaluate the clinical characteristics of patients infected with COVID-19 and the prevalence of comorbidities, as well as the risk of potential diseases in severe patients (or deceased patients) compared with non-severe patients (or survivors). As of July 31, 2020, we had used several databases for literature search. A random effects model was used to summarize the prevalence, odds ratio (OR) and 95% confidence interval (95% CI). The final meta-analysis included 79 studies, analyzing a total of 330,464 infected patients from countries in Asia, Europe and North America. The meta-analysis results showed that the average age of the patients was 55.46 years old, and there were more male patients than females. The most common clinical symptoms were fever, followed by cough, dyspnea, fatigue, sore throat, headache and diarrhea. Hypertension, diabetes and cardiovascular disease were the most common complications. In addition, chronic kidney disease, respiratory disease, cancer, chronic liver disease and HIV often appeared. We also observed that the prevalence of some clinical symptoms and complications varies from region to region. When compared with non-severe patients, the combined odd ratios of some comorbidities were all higher in severe patients. A comparison between deceased and surviving patients found that there was also a higher risk of comorbidities in deceased patients. Our research showed that comorbidities may be a risk factor that affects the development of COVID-19 into severe illness or death. We recommended that high-risk patients adopt more targeted infection prevention and treatment strategies to reduce the risk of future COVID-19 diseases.