Accounting for Imported Cases in Estimating the Time-Varying Reproductive Number of Coronavirus Disease 2019 in Hong Kong

Tim K Tsang; Peng Wu; Eric H Y Lau; Benjamin J Cowling

doi:10.1093/infdis/jiab299

Accounting for Imported Cases in Estimating the Time-Varying Reproductive Number of Coronavirus Disease 2019 in Hong Kong

J Infect Dis. 2021 Sep 1;224(5):783-787. doi: 10.1093/infdis/jiab299.

Authors

Tim K Tsang^{1

2}, Peng Wu^{1

2}, Eric H Y Lau^{1

2}, Benjamin J Cowling^{1

2}

Affiliations

¹ World Health Organization Collaborating Centre for Infectious Disease Epidemiology and Control, School of Public Health, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong Special Administrative Region, China.
² Laboratory of Data Discovery for Health Limited, Hong Kong Science and Technology Park, New Territories, Hong Kong Special Administrative Region, China.

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, accounting for imperfect contact tracing of cases. We applied this framework to data on coronavirus disease 2019 outbreaks in Hong Kong. The estimated Rt for local cases rose above 1 in late March 2020, which was undetected by other commonly used methods. When imported cases account for a considerable proportion of all cases, their impact on estimating Rt is critical.

Keywords: COVID-19; imported cases; reproductive number; transmissibility.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

COVID-19 / epidemiology*
Contact Tracing / methods
Disease Outbreaks
Hong Kong / epidemiology
Humans
SARS-CoV-2 / pathogenicity

Abstract

Publication types

MeSH terms

Grants and funding