Global pandemic modeling for international propagation of COVID-19

Abstract:

Epidemic modeling is a vital tool for understanding, tracking, and mitigating the ongoing global COVID-19 pandemic. While conventional SEIR-type (Susceptible-Exposed-Infectious-Recovered) models have been widely developed to provide insights of the dynamic characteristics of the pandemic, they are often applied to individual countries, cities, or other types of local regions of interests. The evolution of the pandemic in the context of global transmission and its impact to different countries have not been well reported.

To model the global progression of the pandemic and to understand the international effect of one country's policy, we develop a simplified SEI model, with a connectivity matrix which describes the import and export of a portion of the infectious population internationally. The connectivity matrix is constructed based on the air traffic data prior to the pandemic, scaled by 1% to represent the reduction of global travel. Each country is modelled with a homogeneous, well-mixed population, in which the basic reproduction number varies in time according to the policy each country adopts at any given time. We use the stringency index developed by Oxford University to model the pandemic spread in the first half of 2020. Keeping the policy as it is today, we predict the future evolution of the pandemic for the coming year.

Our results (Figure 1) show that significant number of infections are expected in the second half of 2020 and continue to 2021, if no vaccine is developed. The second wave is primarily due to the international transmission of the virus via passenger and merchandise exchange. Such pressure is much higher in Asia countries such as Singapore and South Korea who took strong measures to keep the initial infection low. European countries such as Sweden and UK are expected to suffer less for the second wave due to the community immunity that have built during the first wave of spread.