Transmission Dynamics of COVID-19 in Mainland China: Impact of Public Health Control Measures
28 Pages Posted: 24 Mar 2020More...
Background: The ongoing outbreak of COVID-19 is challenging the Chinese public health response system. We aim to understand the epidemic dynamics and underlying mechanisms, and quantify impact of interventions.
Methods: We estimated attack rate (AR) at county level, mapped spatiotemporal dynamics, and identified risk factors involved in the transmission. We then characterized the epidemic range using boundary analysis, and tracked the effective reproduction number Rt in relation to important events and control measures.
Findings: The ARs were negatively correlated with the distances between affected counties and the epicenter Wuhan. The counties being intersected by railways, freeways, or national highways had significantly higher risk for COVID-19. The number of boundaries, within which active transmission was occurring, rapidly increased up to 698 on Jan 29, 2020. Then, the number dropped and maintained around 300, although the number of cases per boundary consistently increased. The overall Rt waved from 2·7 to 4·0 at the early stage before Dec 31, 2019, when the Wuhan Health Committee announced the outbreak. Thereafter, Rt fluctuated around 3·0 and persisted till Jan 26, when the Chinese authorities took full control of all activities to combat the outbreak. Within a two-week period, the Rt consistently fell to below one on Feb 9. The Rts among different provinces were classified into four clusters.
Interpretation: The strong political commitment and centrally coordinated response are playing the most important role in containing COVID-19 in mainland China.
Funding Statement: This work is supported by the Natural Science Foundation of China (81621005 and 81673238) and National Key Research and Development Program of China (2019YFC1200505).
Declaration of Interests: The authors declare no competing interests.
Ethics Approval Statement: The authors stated that as this study constituted data analysis rather than research in human beings, ethical approval from institutional review boards was not required.
Keywords: COVID-19; China; Transmission dynamics; attack rate; effective reproduction number Rt; public health control measures
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