Introduction
In December 2019, several cases of novel coronavirus-infected pneumonia have been reported in Wuhan, a large city of 11 million people in China [1-3]. Then, the novel coronavirus was identified by the Chinese Center for Disease Control and Prevention from the throat swab and bronchoalveolar lavage fluid samples of patients in Wuhan, and was next named COVID-19 by WHO [4]. The disease spread rapidly from Wuhan to other parts of China. As of March 31, 2020, about 82,545 COVID-19-infected patients in China have been confirmed. More than 50 countries have reported confirmed cases worldwide. Most patients have mild symptoms and good prognosis, while a few develop severe pneumonia, acute respiratory distress syndrome (ARDS), multiple organ failure, or even death.
At present, several observational studies have offered information regarding the epidemiology and clinical features of pneumonia caused by COVID-19[5-13] Clinical manifestations of patients with COVID-19-infected pneumonia mainly include fever, headache, muscle ache, cough, dyspnea, fatigue, etc. A few patients developed ARDS, and multiple organ failure (eg. shock, acute cardiac injury, and acute kidney injury). However, data from different studies also showed significant differences in the incidence of fever, cough, dyspnea, etc. Huang et al found that the most common symptoms were fever (98.6%), fatigue (69.6%), and dry cough (59.4%) at onset of illness [6]. Less common symptoms were dizziness, headache, abdominal pain, etc. Guan et al revealed that only a few patients had symptoms of fever (43.8%) at onset of illness [10]. Accordingly, there are doubts about the clinical significance of differences reported in the different studies. We set out to meta-analyses of all available data from observational studies in China to enable an objective reappraisal of the clinical characteristics.