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

  1. Ka Chun Chong
  2. Wei Cheng
  3. Shi Zhao
  4. Feng Ling
  5. Kirran N. Mohammad
  6. Maggie Wang
  7. Benny CY Zee
  8. Lai Wei
  9. Xi Xiong
  10. Hengyan Liu
  11. Jingxuan Wang
  12. Enfu Chen

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Abstract

Monitoring the reproduction number ( R t ) of the disease could help determine whether there is sustained transmission in a population, but areas with similar epidemic trends could have different transmission dynamics given the risk from imported cases varied across regions. In this study, we examined the R t of coronavirus disease 2019 (COVID-19) by taking different dynamics of imported cases into account and compared the transmissibility of COVID-19 at different intervention periods in Hangzhou and Shenzhen.

Methods

We obtained the daily aggregated counts of laboratory-confirmed imported and local cases of COVID-19 infections in Hangzhou and Shenzhen from January 1 to March 13, 2020. Daily R t and piecewise R t before and after Wuhan lockdown were estimated, accounting for imported cases.

Results

Since the epidemic of COVID-19 in Shenzhen was dominated by imported cases, R t was around 0.1 to 0.7 before the Wuhan lockdown. After the lockdown of Wuhan and the initialization of measures in response to the outbreak, local transmission was well-controlled as indicated by a low estimated value of piecewise R t , 0.15 (95% CI [0.09–0.21]). On the contrary, R t obtained for Hangzhou ranged from 1.2 to 4.9 with a piecewise R t of 2.55 (95% CI [2.13–2.97]) before the lockdown of Wuhan due to the surge in local cases. Because of the Wuhan lockdown and other outbreak response measures, R t dropped below unity in mid-February.

Conclusions

Even though Shenzhen had more cases than Hangzhou, local transmission did not sustain probably due to limited transmission from imported cases owing to the reduction in local susceptibles as residents left the city during Chunyun. The lockdown measures and local outbreak responses helped reduce the local transmissibility.

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  1. Version published to 10.7717/peerj.10350
  2. ScreenIT

    SciScore for 10.1101/2020.03.15.20036541: (What is this?)

    Please note, not all rigor criteria are appropriate for all manuscripts.

    Table 1: Rigor

    NIH rigor criteria are not applicable to paper type.

    Table 2: Resources

    No key resources detected.

    Results from OddPub: We did not detect open data. We also did not detect open code. Researchers are encouraged to share open data when possible (see Nature blog).

    Results from LimitationRecognizer: We detected the following sentences addressing limitations in the study:
    Our study has several major limitations. Recent studies have successively reported that some patients infected with COVID-19 might infect others before their symptom onset [24,34]. Disease transmission during the pre-symptomatic stage implies the possibility of having a negative value of serial interval. This would affect the formulation of estimation equation since the distributional assumption did not gave it a corresponding probability. Alternatively, a generation interval could be used but it is usually hard to be estimated due to unobserved infectiousness onset. Nevertheless, our sensitivity analysis demonstrated that the variation of serial interval within a reasonable range did not affect our main conclusion. Another limitation is the underreporting of confirmed cases due to the unavailability of virological testing in the early stage of epidemic. According to an early investigation [35], an estimate of 75_thousand individuals were found to be infected in Wuhan as of 25 January and we believe similar underreporting was likely to occur in our setting. With detailed data available on reporting rates and serological surveillance, our analytic frame can be extended to a more complex context that incorporates these factors. In addition, our estimates shall be refined if more updated knowledge of the pathogen is available. In conclusion, we showed the lockdown measures and local outbreak responses helped reduce the potential of local transmission in Hangzhou and Shenzhen. Th...

    Results from TrialIdentifier: No clinical trial numbers were referenced.

    Results from Barzooka: We did not find any issues relating to the usage of bar graphs.

    Results from JetFighter: We did not find any issues relating to colormaps.

    Results from rtransparent:
    • Thank you for including a conflict of interest statement. Authors are encouraged to include this statement when submitting to a journal.
    • Thank you for including a funding statement. Authors are encouraged to include this statement when submitting to a journal.
    • No protocol registration statement was detected.

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  3. Version published to 10.1101/2020.03.15.20036541 on medRxiv