Asymptomatic patients as a source of COVID-19 infections: A systematic review and meta-analysis

Int J Infect Dis. 2020 Sep:98:180-186. doi: 10.1016/j.ijid.2020.06.052. Epub 2020 Jun 17.


Background: Coronavirus Disease 2019 (COVID-19) is characterized by an unpredictable disease course, ranging from asymptomatic to severe, life-threatening infections. Asymptomatic COVID-19 infections have been described, and the aim of this systematic review was to summarise their presentation forms.

Methods: We searched PubMed® and Google® (1 December 2019 to 29 March 2020) and extracted age, laboratory findings, and computed tomography (CT) scans. Pooled incidence rates of clinical characteristics were analyzed using random-effect models.

Results: In total, 506 patients from 34 studies (68 single cases and 438 from case-series) with an asymptomatic course were identified. Patients with normal radiology were younger (19.59 ± 17.17 years) than patients with abnormal radiology (39.14 ± 26.70 years) (p-value = 0.013). Despite being asymptomatic, CT investigations revealed abnormalities in 62.2% of the cases; ground-glass opacities were most frequently observed (43.09% by meta-analysis). Most studies reported normal laboratory findings (61.74% by meta-analysis).

Conclusions: More than half of the patients without any symptoms present with CT abnormalities. Asymptomatic patients may be contagious and thus a potential source of transmission of COVID-19.

Keywords: Asymptomatic; Coronavirus disease-19 (COVID-19); Meta-analysis; SARS-CoV-2.

Publication types

  • Meta-Analysis
  • Systematic Review

MeSH terms

  • Betacoronavirus*
  • COVID-19
  • Coronavirus Infections* / diagnostic imaging
  • Disease Progression
  • Humans
  • Pandemics*
  • Pneumonia, Viral* / diagnostic imaging
  • SARS-CoV-2
  • Tomography, X-Ray Computed