Observations about symptomatic and asymptomatic infections of 494 patients with COVID-19 in Shanghai, China

BACKGROUND: Humans are generally susceptible to SARS-CoV-2, which has caused a global pandemic of COVID-19. The screening of infected people in the population still mainly depends on clinical symptoms. However, there is limited research on the characteristics of clinical symptoms in different populations, especially in imported cases. METHODS: To retrospectively analyze the clinical data of 494 confirmed COVID-19 patients admitted to a designated hospital in Shanghai from January 20, 2020, to March 31, 2020, we compared the clinical manifestations in different populations and their influencing factors in COVID-19 patients. RESULTS: (1) Of the 494 patients, 453 (91.7%) had different symptoms at admission, and 39 (7.89%) patients were asymptomatic. (2) We compared the symptoms of patients according to different stratifications and found the following results: (a) The proportion of dyspnea was significantly higher in male patients than in female patients (P < .05). (b) The proportions of a stuffy nose, sore throat, and olfactory and gustatory dysfunction were significantly higher in children than in adult patients (P < .05). (c) The proportions of fever, chest tightness, shortness of breath, and fatigue were significantly higher in local cases than in imported cases. In comparison, the proportions of nasal congestion, stuffy nose, sore throat, headache, and olfactory and gustatory dysfunction were significantly lower in imported cases than in imported cases (P < .05). (d) The proportions of chest tightness, shortness of breath, and dyspnea were significantly higher in severely ill patients than in those with mild symptoms (P < .05). (3) Thirty-one asymptomatic patients were significantly younger than symptomatic patients, and they had a higher proportion of imported cases, white blood cell and lymphocyte count levels, and fewer abnormal CT cases than the group of symptomatic patients (P < .05). (4) The number of days since the onset of the disease needed for the symptoms to disappear was associated with the epidemiological history (imported cases), the number of days until the pharyngeal swab nucleic acid test turned negative, the days of hospitalization, the days of onset, and the white blood cell and lymphocyte count levels (P < .05). CONCLUSIONS: The majority of COVID-19 patients (91.7%) had early symptoms, whereas 7.89% of COVID-19 patients were asymptomatic. Younger patients had fewer symptoms, mainly the upper respiratory symptoms, and the illness condition was milder, which was more common in imported cases. Elderly male patients had severe symptoms when admitted. The number of days needed for the patient's symptoms to disappear was closely related to the number of days necessary for the pharyngeal swab nucleic acid test to turn negative.