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

Andreas Kronbichler, Daniela Kresse, Sojung Yoon, Keum Hwa Lee, Maria Effenberger, Jae Il Shin

Research output: Contribution to journalArticlepeer-review

230 Citations (Scopus)


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.

Original languageEnglish
Pages (from-to)180-186
Number of pages7
JournalInternational Journal of Infectious Diseases
Publication statusPublished - 2020 Sept

Bibliographical note

Publisher Copyright:
© 2020 The Authors

All Science Journal Classification (ASJC) codes

  • Microbiology (medical)
  • Infectious Diseases


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