The geodynamics of pandemics
Geographically speaking, the term pandemic refers to an epidemic that affects the entire world. The prefix « pan » refers to the idea of totality. However, the term pandemic is not only used in the context of an after-the-fact observation to say that an epidemic has spread to the entire planet. On the contrary, one of the challenges of the geographical analysis of epidemics, particularly from the perspective of forecasting, is the ability to identify the origin of a possible pandemic in a localized epidemic phenomenon somewhere on the planet, that is an epidemic spreading worldwide, a global epidemic. In other words, how can we speak of a pandemic before the end of an epidemic? Can we speak of a pandemic other than by observing a posteriori the extent of an epidemic?
This is where a certain amount of geographical intelligence about epidemics can be very useful. Because an epidemic is a phenomenon whose geography is not as simple as it seems.
What makes a virus unfriendly is partly related to a particular form of geography: a virtual geography. In practice, the « pan » of a pandemic refers rather to an anticipation on the part of observers, the idea that one has shortly after the start of the epidemic of its geography in fine. And one might be tempted to add: of the geography of humanity in fine.
It is on the basis of this geography in the making – this supposed geography – that an epidemic becomes a pandemic in the mouths of observers.
But to this virtual geography is added another, which is the spatial signature of the epidemic. For each pathogenic agent has its own mode of dissemination (physical mode of transmission, speed of deleterious action – lethal in particular –, duration of the asymptomatic period, period of contagiousness, etc.) which, combined with its intrinsic lethality (the risk of dying once infected and then affected by the disease) define its own geography. In the case of CoV-2-SARS, the lethality does not appear to be very high compared to other pathogens such as Ebola, which kills infected patients so quickly and frequently that it does not have time to spread, provided localized containment measures are taken. SARS-CoV-2, on the other hand, takes its time and kills little; but it goes far. Since it is quite contagious, it can be transmitted to a large number of people relatively quickly, especially since the period during which one is unknowingly contagious is quite long. It is therefore understandable that this mode of transmission – one could say this spatial mode of existence – corresponds a geography that can cover the entire world, especially in a World constantly criss-crossed by flows of people, some of whom are carriers of the virus without their knowledge. If one were to ask the virus for its passport (it has been discussed…), one could say that, what would constitute part of its identity is this geography of the disease, an identity card that would be a geographical map.
And, once known, this geographical identity would inform us about the future pandemic nature of an epidemic that is starting somewhere.
But the term pandemic has not finished surprising us. Because the geography of a pathogen, while it promises global development, must also be understood in a dynamic way. In other words, over time. A pandemic is also a space-time. It happens. It takes place somewhere at one point in time, then somewhere else later. So the « pan » of a pandemic is never realized, at no time is the pandemic at the same stage everywhere. It will only have been a pandemic to the extent that, in every (or almost every) inhabited place on earth, it will have been an epidemic at some point.
Unlike other phenomena, whose geography is characterized by their spread and then persistence where they have « passed », most of the time an epidemic is just passing through. It is like the flames of a bush fire. From an outbreak, it spreads to the neighborhood, but is no longer active in the affected areas after a certain period of time. Having killed a large or small proportion of the population (modulated by both its virulence and the protective measures available – ranging from no vaccine to no masks in reserve), the virus no longer finds hosts to infect and no longer replicates. So this time it is the geography of the world, the interconnectedness of places and the vulnerability of the populations encountered by the virus, to varying degrees, that will serve as the blueprint for the « epidemic front ».
To illustrate this third geographical dimension of pandemics, we can refer to the beautiful simulation of a pandemic produced by Professor Dirk Brockmann and his team at the Institute for Theoretical Biology (ITB) of Humboldt University (Berlin).
Even if this dynamic cartography is not that of a real historical pandemic, it imitates its geography by using the spatiality of the virus, this geographical identity whose aspects we have explored, by injecting it somewhere on the planet. We can then see the pandemic unfolding at a pace that varies greatly: slow at first, then lightning, then calmer, by drawing geographical patterns which follow the streamlines of contemporary global mobility while presenting complex fluctuations, notably according to the chosen epicenter and the spaces encountered along the way by the virus.
Because of its fundamentally geographical dimension, a pandemic is therefore an extremely interesting tool for the geographer, in that it updates the structure and functioning of the World. And contrary to a classical cartography, it reveals the World without missing its spatiality, i.e. the ways in which it is inhabited and lived. Not bad for an itinerant killer!