https://doi.org/10.1140/epjds/s13688-026-00639-0
Research
The global dissemination of COVID-19 through two coexisting international transmission patterns
1
Graduate School of Information Science, University of Hyogo, Kobe, Japan
2
Center for Computational Science, RIKEN, Kobe, Japan
a
This email address is being protected from spambots. You need JavaScript enabled to view it.
Received:
18
August
2025
Accepted:
3
March
2026
Published online:
16
March
2026
Abstract
The novel coronavirus SARS-CoV-2 and the disease it causes, COVID-19, triggered a global pandemic. Although understanding international transmission dynamics is essential, inferring diffusion networks from observational data remains challenging due to their inherent complexity. In this study, we investigated the global transmission process, including temporal delays, using worldwide COVID-19 case data from January 3, 2020, to December 31, 2022. We analyzed the data using Complex Hilbert Principal Component Analysis, which captures both concurrent relationships and lead-lag dynamics. We then examined interactions among countries with respect to six factors: geography, population, GDP, stringency of countermeasures, vaccination rates, and government type. The results reveal that two primary trends coexisted throughout the period, one in 2020 and another in 2021–2022, with their dominance alternating over time. Specifically, in 2020, European, high-income, and democratic countries led the first trend and were typically associated with higher transmission levels. In contrast, in 2021 and 2022, countries in Africa and the Americas, particularly those with lower income levels, emerged as leading contributors to the second trend. We also found that, while internal countermeasures may have helped suppress domestic infection levels, they did not affect the international transmission pattern. Furthermore, although vaccination became widespread in 2021, it did not alter the pattern of international spread.
Key words: COVID-19 / Interactions / Principal component analysis / Infection spread / Country
Supplementary Information The online version contains supplementary material available at https://doi.org/10.1140/epjds/s13688-026-00639-0.
Handling Editor: Daniela Paolotti
© The Author(s) 2026
Open Access This article is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License, which permits any non-commercial use, sharing, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if you modified the licensed material. You do not have permission under this licence to share adapted material derived from this article or parts of it. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by-nc-nd/4.0/.
