IFISC researchers discover critical link between mobility and epidemic spread

• A new study, led by IFISC researchers,  studies epidemics in light of a critical mobility threshold that can trigger major epidemic outbreaks.
• This research provides valuable information for the design of mobility-based epidemic containment strategies, with significant implications for public health and policy-making.

How do epidemic containment policies shape an epidemic? A novel study published in Scientific Reports  studies epidemic containment policies in light of the critical level of mobility, the population’s mobility level at which major outbreaks can be triggered, offering new perspectives on how human and political behavior influences the spread of infectious diseases. The research, led by the Institute for Cross-Disciplinary Physics and Complex Systems (IFISC, CSIC-UIB), sheds light on this complex relationship, with implications for designing more effective containment strategies.

The study was conducted by a team of researchers from IFISC in collaboration with Kido Dynamics SA, the Institute for Applied Mathematics Mauro Picone (IAC), and the Centro Studi e Ricerche Enrico Fermi (CREF). Together, they developed an agent-based model to simulate the interplay between mobility and social contacts. "We discovered how epidemic containment policies such as COVID-19 traffic light systems shape an epidemic via interaction with the critical mobility level" explains Jesús Moreno, lead author of the study. "This finding has significant implications for the design of epidemic containment strategies."

The researchers modeled their agents after anonymized cell phone mobility data from 13 million users in Spain over 42 weeks, spanning from January 2020 to October 2024. "Using such a large-scale, real-world dataset allowed us to base our theoretical model on actual human behavior patterns observed during key phases of the COVID-19 pandemic" adds Ramasco, senior researcher at IFISC.

The study examined two main types of non-pharmaceutical interventions: traffic light policies and critical mobility inspired interventions. Traffic light interventions created an oscillating pattern in the epidemic's progression, with alternating periods of higher and lower transmission. This strategy, if performed fast enough, helped flatten the curve and prevent unmanageable spikes in cases, whilst if done hesitantly can aggravate the situation Meanwhile, critical mobility based restrictions proved particularly effective. By limiting movement when mobility exceeded the critical threshold identified in the study, researchers demonstrated that it was possible to significantly reduce transmission rates and maintain control of the epidemic without resorting to erratic opening and closures. “Both interventions, when applied strategically, showed potential to guide the epidemic into a more manageable state, but only those who consider the critical mobility level manage to balance both public health concerns and socio-economic considerations”, says Moreno.

The researchers emphasize that their model, while simple, captures the essence of the relationship between mobility and social contacts. "Our findings underscore the importance of considering the critical aspect of mobility in epidemic containment strategies" explains Ramasco. "This could help policymakers make more informed decisions to minimize strain on the healthcare system while balancing economic and social factors”.

This research provides a new perspective on the role of mobility in epidemic dynamics and lays the groundwork for future studies exploring the factors driving these patterns. By advancing our understanding of epidemic spread, the study offers valuable insights for policymakers and public health professionals striving to protect citizens from infectious diseases. “Integrating mobility data into public health policies could be a game-changer in preventing catastrophic outbreaks”, concludes Moreno.

Moreno López, J.A., Mateo, D., Hernando, A. et al. Critical mobility in policy making for epidemic containment. Sci Rep 15, 3055 (2025). https://doi.org/10.1038/s41598-025-86759-5

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