Lichao Yang’s research while affiliated with Tsinghua University and other places

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Publications (1)

Improved SIR model on SARS-CoV-2 transmission. Dashed lines are influence parameters refer to a real-world scenario where the untraceable infections were reported. For example, untraceable infections that caused by contaminated cold-chain products θ2 and infections rate θ1(t) that trigger local outbreaks. Solid lines are transition probability of compartments. Parameters α0(t), λ, δi and δq are related to the NPIs implemented for China-bound travelers and α1, α2, and α3 are the outbound parameters; ri,di are the recovery rate and qr is the death rate; p, β, ε, eq, qi are the transition probability. Furthermore, the arrows represent the direction of transition/influence between compartments. With above, the initial values and detailed values are presented in Tables 1, 2.
(A–D) Model fitting and real-world data comparison. Panels (A–D) were the verification results of model parameters inputting, compared existing symptomatic cases, existing suspected cases, existing asymptomatic cases, and cumulative recovered individual datasets, from July 21, 2021 to August 30, 2021 based on the National Health Commission of China reports. Additionally, dotted lines were the 95%CI of prediction results, solid lines were the prediction results by model inputting, and original points were the statistical data from the National Health Commission of China reports. Moreover, the RMSE of (A) is equal to 194.35; the RMSE of (B) is equal to 6733.59; the RMSE of (C) is equal to 46.54; and the RMSE of (D) is equal to 283.57.
(A–I) Health resource demand prediction based on number of inbound flights. Panels (A–C) show the demand for hospital beds, PCR tests, and isolation rooms in a real-world scenario where the daily inbound flight is equal to 79. Panels (D–F) simulate the changes when inbound flights are 160, a scenario where the current requirements have been slightly lifted. Panels (G–I) present results when the number of inbound flights is 1,366, a scenario with no inbound flight restrictions.
The validity period setting of PCR test vs. infected cases count.
The number of inbound flights vs. infected cases count.

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The impact of multiple non-pharmaceutical interventions for China-bound travel on domestic COVID-19 outbreaks
  • Article
  • Full-text available

July 2023

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26 Reads

Lichao Yang

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Mengzhi Hu

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Huatang Zeng

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[...]

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Jiming Zhu

Objectives Non-pharmaceutical interventions (NPIs) implemented on China-bound travel have successfully mitigated cross-regional transmission of COVID-19 but made the country face ripple effects. Thus, adjusting these interventions to reduce interruptions to individuals’ daily life while minimizing transmission risk was urgent. Methods An improved Susceptible-Infected-Recovered (SIR) model was built to evaluate the Delta variant’s epidemiological characteristics and the impact of NPIs. To explore the risk associated with inbound travelers and the occurrence of domestic traceable outbreaks, we developed an association parameter that combined inbound traveler counts with a time-varying initial value. In addition, multiple time-varying functions were used to model changes in the implementation of NPIs. Related parameters of functions were run by the MCSS method with 1,000 iterations to derive the probability distribution. Initial values, estimated parameters, and corresponding 95% CI were obtained. Reported existing symptomatic, suspected, and asymptomatic case counts were used as the training datasets. Reported cumulative recovered individual data were used to verify the reliability of relevant parameters. Lastly, we used the value of the ratio (Bias²/Variance) to verify the stability of the mathematical model, and the effects of the NPIs on the infected cases to analyze the sensitivity of input parameters. Results The quantitative findings indicated that this improved model was highly compatible with publicly reported data collected from July 21 to August 30, 2021. The number of inbound travelers was associated with the occurrence of domestic outbreaks. A proportional relationship between the Delta variant incubation period and PCR test validity period was found. The model also predicted that restoration of pre-pandemic travel schedules while adhering to NPIs requirements would cause shortages in health resources. The maximum demand for hospital beds would reach 25,000/day, the volume of PCR tests would be 8,000/day, and the number of isolation rooms would reach 800,000/day within 30 days. Conclusion With the pandemic approaching the end, reexamining it carefully helps better address future outbreaks. This predictive model has provided scientific evidence for NPIs’ effectiveness and quantifiable evidence of health resource allocation. It could guide the design of future epidemic prevention and control policies, and provide strategic recommendations on scarce health resource allocation.

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