Contagion and diffusion are related concepts that are often best understood through network analysis. The use of network graphs can help you provide considerable insight into the potential spread of a disease as well as the success of a new innovation. This is done by exposing the structure of the underlying network. Densely connected networks can be effective in both of these realms, which can have both positive and negative effects, depending on whether we are viewing the diffusion of a positive innovation, or conversely, the spread of an infectious disease.
One of the most intriguing and potentially valuable ways of using networks is to examine how disease transmission works within a network, and how the structure of a network can either promote or limit the spread of the disease. If the transmission pattern can be altered through some sort of intervention, such as vaccination or even simple avoidance (for example, not contacting a friend if there is a...