Comparison of clinical and epidemiological characteristics of asymptomatic and symptomatic SARS-CoV-2 infection: A multi-center study in Sichuan Province, China

Abstract

Objectives: Asymptomatic infection of SARS-CoV-2 has become a concern worldwide. This study aims to compare the epidemiology and the clinical characteristics of SARS-CoV-2 infection in asymptomatic and symptomatic individuals.

Methods: A total of 511 confirmed SARS-CoV-2 infection cases, including 100 asymptomatic (by the time of the pathogenic tests) and 411 symptomatic individuals were consecutively enrolled from January 25 to February 20, 2020 from hospitals in 21 cities and 47 counties or districts in Sichuan Province. Epidemiological and clinical characteristics were compared.

Results: Compared to the symptomatic patients, the asymptomatic cases were younger (P < 0.001), had similar co-morbidity percentages (P = 0.609), and came from higher altitude areas with lower population mobility (P < 0.001) with better defined epidemiological history (P < 0.001). 27.4% of well-documented asymptomatic cases developed delayed symptoms after the pathogenic diagnosis. 60% of asymptomatic cases demonstrated findings of pneumonia on the initial chest CT, including well-recognized features of coronavirus disease-19. None of the asymptomatic individuals died. Two elderly individuals with initially asymptomatic infection developed severe symptoms during hospitalization. One case of possible virus transmission by a patient during the incubation period was highly suspected.

Conclusions: The epidemiological and clinical findings highlight the significance of asymptomatic infection with SARS-CoV-2. Inspecting the epidemiological history would facilitate the identification of asymptomatic cases. Evidence supports the chest CT scans for confirmed asymptomatic cases to evaluate the extent of lung involvement.

Keywords: Asymptomatic; Clinical characteristics; Coronavirus disease-19; Epidemiology; SARS-CoV-2.

Fig. 1

Flow diagram of subject inclusion.

Fig. 2

The plot of time versus number of cases in two groups.

Fig. 3

A case from asymptomatic group. A 35 years old male who lived in an infected area where COVID-19 cases had been reported. He was tested positive for COVID-19 by nucleic acid test by throat swab sampling from home. The patient showed no recent symptoms. Chest CT showed bilateral and peripherally distributed ground glass opacities.

Fig. 4

A case from asymptomatic group. A 53 years old female who lived at an infected area where COVID-19 cases had been reported. She tested positive for COVID-19 by nucleic acid test but showed no symptoms at the time of the CT scan, and had abdominal discomfort 10 days after the scan. Chest CT showed bilateral, multiple ground glass and consolidative pulmonary opacities.