Simulating the impacts of interregional mobility restriction on the spatial spread of COVID-19 in Japan

Abstract

A spatial susceptible–exposed–infectious–recovered (SEIR) model is developed to analyze the effects of restricting interregional mobility on the spatial spread of the coronavirus disease 2019 (COVID-19) infection in Japan. National and local governments have requested that residents refrain from traveling between prefectures during the state of emergency. However, the extent to which restricting interregional mobility prevents infection expansion is unclear. The spatial SEIR model describes the spatial spread pattern of COVID-19 infection when people commute or travel to a prefecture in the daytime and return to their residential prefecture at night. It is assumed that people are exposed to an infection risk during their daytime activities. The spatial spread of COVID-19 infection is simulated by integrating interregional mobility data. According to the simulation results, interregional mobility restrictions can prevent the geographical expansion of the infection. On the other hand, in urban prefectures with many infectious individuals, residents are exposed to higher infection risk when their interregional mobility is restricted. The simulation results also show that interregional mobility restrictions play a limited role in reducing the total number of infected individuals in Japan, suggesting that other non-pharmaceutical interventions should be implemented to reduce the epidemic size.

Role of stay-at-home requests and travel restrictions in preventing the spread of COVID-19 in Japan

“…A great number of people commute between different prefectures in the Tokyo Megalopolis Region, which promotes the spatial transmission of COVID-19 across prefectures. Massive inter-prefectural commuting also leads to different population compositions in each prefecture in the daytime and nighttime, so we separated the transmission equations into two parts inspired by Pei et al, 2018 , Kondo, 2021 .…”

“…Note that we treat inter-prefectural random visitors in the same way as inter-prefectural commuters for the sake of simplicity. Additionally, the spatial distribution of infectious individuals affects the risk of infection in each prefecture ( Kondo, 2021 ). The number of presymptomatic infectious, undocumented infectious, documented infectious individuals in prefecture j during the daytime on day t , denoted as , , and , respectively, can be estimated as , , and , and the population in prefecture j during the daytime is .…”

“…To characterize the transmission of COVID-19, compartmental models have been widely used because of their well-explored mathematical properties and scalability at the city level ( Ding et al, 2021 , Kondo, 2021 , Qian and Ukkusuri, 2021 ). The most basic compartmental model is the susceptible-infectious-removed (SIR) model, which divides the population into susceptible, infectious, and removed compartments.…”

Exploring spatiotemporal patterns of COVID-19 infection in Nagasaki Prefecture in Japan using prospective space-time scan statistics from April 2020 to April 2022

“…The third wave (Period 2) of COVID-19 in Nagasaki Prefecture started in early December 2020, roughly 1 month later than in prefectures with big cities like Tokyo, Osaka, and Fukuoka [ 30 ], even though the local and national governments requested residents to avoid unnecessary travel between prefectures, especially those from prefectures with high infection risk. Mild restrictions policies, however, could not restrain the disease transmission because interregional mobility speeded up infection’s geographical expansion from urban prefectures with numerous infectious people to rural prefectures [ 31 ]. A “Go-To” campaign to encourage travel and dining out started on July 22, 2020, and a consecutive New Year’s Day (Fig.…”

Problem drinkers and high risk-taking behaviors under the stay-at-home policy of the COVID-19 emergency declaration

“…As for Japan, the government implemented a stay-at-home policy without penalties[ 9 , 10 ] and requested various facilities, including restaurants/bars, to either temporarily close their businesses or shorten their business hours. In particular, the Japanese government asked its people to stay at home and focused on closing businesses that had clusters of COVID-19 before the first emergency declaration.…”