Watching Monty Python the other day, I found my thoughts wandering once again back to Networks 204 and Gladwell’s description of a syphilis epidemic in Baltimore: how it spread from the projects along local highways during summer months and contracted during the winter. Explicitly drawing a connection between contagious viral diseases and transportation networks is essential to understanding the ideas behind the book, especially given the current era of globalization. Six-degrees of separation and small world phenomena is only impressive because of the context of the network population’s massive and ever growing size (6 billion plus people), increasingly connected by aviation, marine, rail and motor-vehicle transport infrastructure.

A recent academic article from the School of Informatics and Center for Biocomplexity at Indiana University developed statistics referring to the spread of contagious diseases like the flu as it passed through links (i.e. flights) to various nodes (i.e. airports). Transportation networks not only diffuse sickness, but also concentrate various people onto a small area, such as airports, seaports, train stations, subway cars, ferries, and so on. This gives the virus ample time and proximity to spread from the host carrier to victims, particularly given the unhygienic nature of these facilities. The interconnectivity not only allows people and (animal) products to move far and quickly, but also transit any viruses that they may be carrying with them.

Natural functions such as migratory patterns are also attributable to the spread of diseases, like the Avian Flu. The Siberian-Caspian-Nile flyway, used as a superhighway by millions of birds, is one such suspected culprit, though others argue that viruses like the Avian Flu will more readily spread through the human engineered transportation network. After all, one would expect diffusion concentrated mainly along the path of the flyway, though empirical evidence has shown otherwise. In other words, the Tipping Point has not (yet) been activated. However, if the disease spread through migratory patterns theory was realized, places like Alaska, where New and Old World birds meet, would create an “international viral transfer center.” Alaska could then be interpreted as a gatekeeper role—one that could be culled in order to stop the spread of a disease by re-dividing (or quarantining) the networks.

Diseases provide interesting network implications in other ways, like power exchange theory and link analysis. Those who are at the center of a network, with more links embedding them in the overall structure, are generally considered to have more power over other nodes. Conversely, they become extremely weak when bombarded with many virus-carrying links during a flu pandemic. On the other hand, those who are at the edges of a network appear less vulnerable through their own self-quarantining habits. Additionally, there is one remaining twist in that those who occupy centralized nodes on a network may become immune to viral diseases due to their proximity and constant contact. During the discovery of the New World, Native Americans were especially vulnerable to European diseases because they were now the outside edges of a large Euro-centric network, whose occupants had millennia to build genetic immunities.

In any case, I’m not dead yet.