Viral Network Analysis
http://www.orgnet.com/contagion.html
http://www.orgnet.com/AIDSNA.pdf
Virus is a term that is associated with quick spreading, and ugly symptoms. Viruses can be either physical, infecting our human bodies, or virtual, infecting our computers and systems. Both have the potential to bring our world to a halt. The spread of these powerful forces can be modeled using the principles of networks and graph theory.
The above links point to a web comic, a graph analysis, and a paper, all written on the subject of contagions and viruses spreading through a network.
I put the web comic here because it is an interesting application of the theory. It is a real time representation of computer viruses spreading throughout a network of computers, while also taking an unrelated crack at the security flaws of windows. The links formed between nodes in the constantly changing network create interesting flow patterns for the viruses to spread.
The second link has more of an actually network graph analysis. It has a graph with nodes of different types. Infectors, carriers, not infected, and unknown people are represented in the graph by different colors. You can see how each infector is at the center of his own sub-graph, and some infectors have even had its ‘children’ form their own sub-graph.
The last link is an in depth study on the spread of HIV in prisons. It provides an interesting perspective on the spread of diseases. It is shown that those infected can be split into ‘clusters,’ which are groups of people who have been infected by the same strain. These clusters are analogous to the sub-graphs seen in the second link. This article is most interesting to me because of the section on how the virus spread from one prison to another, people in the same cluster were found in different prisons. This is shown as a result of inmates getting infected, then either being transferred or getting released and reincarcerated. Single inmates can act as a bridge between the different sub-groups within each cluster (which are themselves sub-groups of the bigger graph of all inmates).
Network analysis and graph theory can help the CDC and other organizations track the spread of disease, and better understand how the spread is structured. Using this information they can do better to stop the spread of diseases in populations.