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Transmissibility of coronavirus disease 2019 in Chinese cities with different dynamics of imported cases

Ka Chun Chong1,2, Wei Cheng3, Shi Zhao1,2

  • 1School of Public Health and Primary Care, The Chinese University of Hong Kong, Hong Kong, China.

Peerj
|November 16, 2020
PubMed

Insights

Local transmission of coronavirus disease 2019 (COVID-19) was controlled by lockdown measures, despite varying imported case dynamics. Shenzhen

Area of Science:

  • Epidemiology
  • Infectious disease dynamics

Background:

  • Monitoring the reproduction number (R) is crucial for assessing disease transmission.
  • Imported cases can significantly influence local transmission dynamics, necessitating region-specific analyses.
  • Understanding varied transmission patterns is key to effective public health interventions.

Purpose of the Study:

  • To examine the reproduction number (R) of coronavirus disease 2019 (COVID-19) in Hangzhou and Shenzhen.
  • To compare COVID-19 transmissibility across different intervention periods, considering imported case dynamics.
  • To evaluate the impact of the Wuhan lockdown and local outbreak responses on transmission.

Main Methods:

  • Collected daily counts of laboratory-confirmed imported and local COVID-19 cases in Hangzhou and Shenzhen (Jan 1–Mar 13, 2020).
  • Estimated daily R and piecewise R values before and after the Wuhan lockdown.
  • Accounted for the influence of imported cases in R estimations.

Main Results:

  • Shenzhen's epidemic was import-dominated (R: 0.1–0.7 pre-lockdown); local transmission was controlled post-lockdown (piecewise R: 0.15).
  • Hangzhou experienced higher local transmission (R: 1.2–4.9 pre-lockdown; piecewise R: 2.55).
  • Wuhan lockdown and response measures reduced R below unity in Hangzhou by mid-February.

Conclusions:

  • Shenzhen's local COVID-19 transmission did not sustain despite higher case numbers, likely due to reduced local susceptibles and controlled imported cases.
  • Lockdown measures and local outbreak responses were effective in reducing local transmissibility in both cities.
  • Region-specific epidemic trends and imported case dynamics are critical for understanding and managing infectious disease spread.
Abstract

Keywords:
COVID-19Reproduction numberSerial intervalTravel restriction

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