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Effective containment explains subexponential growth in recent confirmed COVID-19 cases in China

Our take —

Using mathematical modeling, the authors show that containment policies and social distancing measures effectively slowed the growth in confirmed COVID-19 cases in China.

Study design

Ecological; Modeling/Simulation

Study population and setting

The authors used an SIR model variant to assess the impact of containment strategies and social distancing measures on daily confirmed COVID-19 cases in mainland China between January and February 2020. A range of measures were implemented in China including: 1) quarantining the sick and suspected in hospitals, at home or monitored house arrest; 2) social distancing measures including closing businesses, universities and mandatory curfews in some areas; 3) stricter handwashing guidance and use of masks; and 4) contact tracing.

Summary of Main Findings

The confirmed case trajectories in each province initially followed a rapid exponential growth trajectory, but then slowed down, moving towards a flattened curve. The authors found that adding two features to a Susceptible Infectious Recovered (SIR) model — effectively removing individuals from the susceptible pool through social distancing, handwashing, masks and contact tracing; and removing infected individuals through quarantine — was sufficient to reproduce the shapes of the confirmed case curves.

Study Strengths

The model was simple and parsimonious, and fit observed data well. The model was robust when applied to different provinces in China.

Limitations

The analysis was restricted up to February 12, 2020, as changes to the case definition for COVID-19 led to an increase in the number of cases after this date. As with similar analyses, efficacy of specific mitigation measures were not assessed but rather, an overall average effect is described. Changes in testing strategies were not described in this paper and may impact confirmed case numbers.

Value added

The simple model developed in the study can be applied to epidemics in different areas to assess the impacts of quarantine and social distancing. The study adds to the already large evidence base for the effectiveness of quarantine and social distancing measures in reducing the spread of COVID-19.

This review was posted on: 12 June 2020