Scenario: spatial diffusion of measles in Iceland
Source: A. Cliff, P. Haggett, J. Ord and G. Versey. 1981. Spatial
Diffusion: An Historical Geography of Epidemics in an Island Community,
Cambridge University Press.
Spatial diffusion of disease describes the process by which a disease
concentrated in one location on the Earth's surface spreads out over a wider
area. The general principles that appear to underlie this spread mechanism
in human populations include contagion, waves, corridors, barriers, and
hierarchical structuring. This book tracks and maps one of the most
dramatic of diffusion waves, an epidemic, in terms of the passage of one
common childhood disease that is much studied in the epidemiological
literature, namely that cause by the measles virus. Attention in focused on
the sparsely populated and relatively remote island of Iceland, in order to
control from complexities of spread. Iceland has available a century of
unusually complete records revealing at least sixteen distinct epidemic
waves spreading and ebbing across the island. Specific reference to these
phenomena appear on pp. 55-91.
Principal concepts: hierarchical diffusion (pp. 9, 26-32, 90, 91, 96),
contagious diffusion (pp. 6, 27-32, 90, 91, 96), barriers to diffusion (pp.
22-25), corridors channeling diffusion (pp. 22, 25-26), waves of diffusion
(pp. 37-44, 62-88), models of diffusion (pp. 17-35, 132-183).
Questions:
- Why does measles leap when it diffuses?
- Why are there cycles of measles outbreaks?
- What are the advantages of using maps as well as time series of cases
when studying an epidemic?
- How can maps be used to monitor intervention success?
- What are the barriers and channels for measles diffusion in Iceland?
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