Patchiness of population and the transit of infectious agents between patches, which is related to things like traffic volume and between patch distance are features that in addition to basic characteristics of a disease agent influence the capacity of illness to wipe out a population.
30 years ago, while first considering the spatial modeling of disease I wrote a modification to the "GAME OF LIFE" that well illustrated that. Patches of hosts had surprising persistence. At the time I was interested in the comparative and complimentary roles of disease and over-kill explanations of north American megafauna extinctions.
I quickly learned that getting spatial resolution modeling a virtual world divided into 'cells' needed more computing power than was available on my first PC. I changed my focus and went on to do numerical population modeling of parasitic disease, which was less memory intensive.
In a biological world going molecular I became an undergrad instructor, I never went back to do more work with spatial modeling...But the idea of patchiness of susceptible hosts has always stuck with me. I sort of suspect that socio-economic stratification of society, and various asymmetries of exposure risk (such as vocation/avocation, access to hygiene) are also 'effectors' involved in 'regulating' transit of many diseases between classes (essentially patches) in a society.
As we have seen with HIV-AIDS, social and economic issues between and within cultures can make the presentation of epidemics look rather different.
One of the challenges is that the folks working this epidemic have to learn from what's happening in Africa while realizing that it might not look like what would happen in Australia or the US. And while being leary of applying quickly made assumptions/ generalizations about how things are different which probably leave lots of room for surprises.
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