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Asymptomatic SARS-CoV-2 Carriers: A Systematic Review and Meta-Analysis

  • Syangtan, Gopiram1
  • Bista, Shrijana2
  • Dawadi, Prabin2
  • Rayamajhee, Binod3, 4
  • Shrestha, Lok Bahadur5
  • Tuladhar, Reshma2
  • Joshi, Dev Raj2
  • 1 Shi-Gan International College of Science and Technology (SICOST), Tribhuvan University, Kathmandu , (Nepal)
  • 2 Central Department of Microbiology, Tribhuvan University, Kathmandu , (Nepal)
  • 3 Faculty of Science, School of Optometry and Vision Science (SOVS), University of New South Wales (UNSW), Sydney, NSW , (Australia)
  • 4 Department of Infection and Immunology, Kathmandu Research Institute for Biological Sciences (KRIBS), Lalitpur , (Nepal)
  • 5 Department of Microbiology and Infectious Diseases, B. P. Koirala Institute of Health Sciences, Dharan , (Nepal)
Published Article
Frontiers in Public Health
Frontiers Media SA
Publication Date
Jan 20, 2021
DOI: 10.3389/fpubh.2020.587374
  • Public Health
  • Systematic Review


Asymptomatic cases of SARS-CoV-2 can be unknown carriers magnifying the transmission of COVID-19. This study appraised the frequency of asymptomatic individuals and estimated occurrence by age group and gender by reviewing the existing published data on asymptomatic people with COVID-19. Three electronic databases, PubMed, Embase, and Web of Science (WoS), were used to search the literature following the guidelines of Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA). The study population for this review included asymptomatic individuals infected with SARS-CoV-2 reported in original articles published up to 30 April 2020. A random effects model was applied to analyze pooled data on the prevalence of asymptomatic cases among all COVID-19 patients and also by age and gender. From the meta-analysis of 16 studies, comprising 2,788 SARS-CoV-2 infected patients, the pooled prevalence according to the random effect size of asymptomatic cases was 48.2% (95% CI, 30–67%). Of the asymptomatic cases, 55.5% (95% CI, 43.6–66.8%) were female and 49.6% (95% CI, 20.5–79.1%) were children. Children and females were more likely to present as asymptomatic COVID-19 cases and could act as unknown carriers of SARS-CoV-2. Symptom-based screening might fail to identify all SARS-CoV-2 infections escalating the threat of global spread and impeding containment. Therefore, a mass surveillance system to track asymptomatic cases is critical, with special attention to females and children.

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