Following the COVID-19 pandemic, the world has experienced a clear recovery in international mobility. For months, global travel was drastically reduced, and many experts wondered whether that shock could mark a turning point in the way we move. The pandemic brought alternatives such as teleconferencing and remote work to the forefront, which seemed capable of structurally reducing the need to travel. However, despite initial doubts about whether pre-pandemic levels of hypermobility would return, data show that international mobility continues to grow at a sustained rate of 4–5% per year, in line with pre-pandemic projections. Moreover, a significant proportion of these movements (around 60%) are directed towards temperate regions in Asia, Africa and Latin America. This pattern not only reflects changes in global tourism, but also an intensification of contacts between areas with very different epidemiological realities.
Why international mobility is the main amplifier of emerging diseases
Much has been said about the factors that explain the emergence of new diseases, most of them of zoonotic origin. Land use and deforestation, climate change, intensive livestock farming, demographic pressure and social factors (such as poverty and the presence of weak health systems) are often cited as key elements facilitating the spillover of pathogens from animals to humans. Nevertheless, the determining factor in their global dissemination is hypermobility, which allows humans to travel from one end of the world to the other in less than 24 hours. Just six years ago, the world witnessed how the emergence of a new disease, COVID-19, originating in a localised context, spread to several continents within days thanks to constant flows of international travellers.
Zoonoses and travel: how local pathogens can become global in a matter of days
This same month, a group of people of different nationalities on a cruise ship contributed to transporting a zoonotic disease, the Andes virus—a type of hantavirus—to their respective countries. This episode illustrates how global mobility can act as a multiplying vector, regardless of the nature of the pathogen. And it is not only diseases transmitted directly through air or contact that are susceptible to spreading in this way. In recent years, sporadic cases of dengue have been detected in several European regions. These cases keep public health systems on alert, aware that only the right conditions are needed—such as the presence of the vector and the introduction of the virus through an infected traveller—for sustained local transmission to become established in the Mediterranean.
This is the reality we live with. International mobility is the backbone of the spread of these diseases and is, as we have seen, a structural and hardly reversible phenomenon. Simplifications should be avoided: the global spread of emerging diseases is not primarily associated with slow and sustained migratory movements, but with the intensity and speed of international travel flows.
From early diagnosis to international coordination: how to manage risk
In this context, the question is not how to stop mobility, but how to manage its risks. It is essential to continue addressing the factors that facilitate the spillover of pathogens to humans, despite their complexity and the difficulty of acting on global dynamics. There is frequent reference to the need to coordinate the human, animal and environmental health sectors, but this shared vision rarely translates into effective mechanisms for joint action. The real challenge is not identifying the problem, but ensuring that these actors work together in an integrated and sustained manner, with public administrations playing a key role in promoting this coordination, in close collaboration with the business sector and other private stakeholders.
At the same time, it is crucial to strengthen epidemiological surveillance systems and early warning mechanisms, incorporating tools that significantly enhance our capacity for detection and response, such as digital health, artificial intelligence and advances in diagnostics. Only through rapid detection, international coordination and response capacity will we be able to minimise the impact of future health threats in an inevitably interconnected world.
