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Incubation period of COVID-19: a meta-analysis
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  • Christelle Elias,
  • Abel Sekri,
  • Pierre Leblanc,
  • Michel Cucherat,
  • Philippe Vanhems
Christelle Elias
CIRI
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Abel Sekri
HCL
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Pierre Leblanc
HCL
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Michel Cucherat
HCL
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Philippe Vanhems
CIRI
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Abstract

A valid measurement of the SARS-CoV-2 incubation period is needed for case definitions and for adapting appropriate isolation measures but is challenging in an emergency context. The objective was to systematically review recent literature of reported estimates of the distribution of incubation period of SARS-CoV-2 for describing the distribution and its variability and dispersion through meta-analysis. A systematic review search was carried out up to July 1st 2020 of all identified references available reporting the SARS-CoV-2 incubation. Individual mean and standard deviation were used to produce the pooled estimate. Heterogeneity was also assessed using I2 statistics and sources of heterogeneity were explored using a meta-regression. The main outcome was the SARS-CoV-2 incubation period defined as the time from exposure to onset of clinical illness. In total, 43 studies were eligible, including 12 (27.9%) cohorts and 31 (72.1%) case reports and series. The pooled estimate of the mean incubation period across the studies was 6.24 days, 95% CI [5.80;6.69] ranging from 2.33 to 17.60 days. Shorter incubation periods were reported in cohorts compared to case series (p<0.01) and among studies with high proportions of males (p<0.05). The mean incubation period will help for identification times of exposure but determinants of its variations/range might be explored for potential links with clinical outcome or early pathogenic steps. The impact of individuals with extreme values of incubation on the outbreak dynamic should be evaluated taking account for the basic reproductive number. A real time of meta-analysis, called the InCoVid Lyon, is proposed.