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Oxford University Press - PMC COVID-19 Collection logoLink to Oxford University Press - PMC COVID-19 Collection
. 2021 Jun 4:jiab299. doi: 10.1093/infdis/jiab299

Accounting for imported cases in estimating the time-varying reproductive number of COVID-19 in Hong Kong

Tim K Tsang 1,2,, Peng Wu 1,2, Eric H Y Lau 1,2, Benjamin J Cowling 1,2,
PMCID: PMC8244742  PMID: 34086944

Abstract

Estimating the time-varying reproductive number, Rt, is critical for monitoring transmissibility of an infectious disease. The impact of imported cases on the estimation is rarely explored. We developed a model to estimate separately the Rt for local cases and imported cases, with accounting for imperfect contact tracing of cases. We applied this framework to data on COVID-19 outbreaks in Hong Kong. The estimated Rt for local cases rise above 1 in late March, 2020, which was undetected by other commonly used methods. When imported cases accounted for a considerable proportion of all cases, their impact on estimating Rt is critical.

Keywords: Reproductive number, COVID-19, transmissibility, Imported cases

Supplementary Material

jiab299_suppl_Supplementary_Materials

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Supplementary Materials

jiab299_suppl_Supplementary_Materials

Articles from The Journal of Infectious Diseases are provided here courtesy of Oxford University Press

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