The Dictionary of Human Geography

necessitates an encounter with the discursive
given the impossibility of apprehending an
extra-discursive realm beyond language and
other modes of representation (see
Howarth, Norval and Stavrakakis, 2000).
Here, although few of these authors would pre-
sent their thought in these terms, Roland
Barthes’ examination of mythologies, Jacques
Derrida’s notion of deconstruction and
Michel Foucault’s account of genealogy
would all count as critical analyses of discourse,
even if they could not be understood as
Discourse Analysis. Nor is this broadly defined
critical approach to discourse limited to ques-
tions of language or text (even if they are under-
stood as social practices). As Rose (2007
[2001]) makes clear, discourse analysis is an
important methodology for the study of visual
culture (seevisual methods). dca

Suggested reading
Fairclough (2003). See also the journalDiscourse
and Society.

disease, diffusion of An area ofmedical
geographythat is concerned with mapping
and modelling the spread of infectious dis-
eases and their causative agents (e.g. viruses,
bacteria and protozoa) overspaceand through
time. The approach is characterized by the
application of quantitative techniques to
decipher the spatial and temporal properties
ofepidemicwaves in terms of their timing,
intensity, rate and geographical corridors of
spread (descriptive models), and to apply this
understanding to the prediction of future dis-
ease distributions (predictive models). Particular
concern with the topic stems from a need to
intervene in the spread of epidemic waves (e.g.
through the implementation of quarantine or
vaccination) as part of publichealthpolicy
Geographical interest in the spread of infec-
tious diseases was stimulated by a broader
disciplinary concern with spatial diffusion
that followed from the influential studies of
Torsten Ha ̈gerstrand in the 1950s (see
Haggett, 2000). Within the tradition of diffu-
sion modelling initiated by Ha ̈gerstrand, geog-
raphers have sought to identify the nature of
the diffusion processes by which infectious dis-
eases are propagated spatially, and to incorpor-
ate elements of these processes into formal
mathematicalmodelsof epidemic transmis-
sion. Two basic types of spatial diffusion
process have received particular attention in
the literature. Acontagious processdescribes
the wave-like spread of a disease from its point
of introduction to geographically proximal

centres. Alternatively, a hierarchical process

describes the spread of a disease through an

ordered sequence of classes or places (e.g. an

urban settlement hierarchy). Spatial diffusion

processes of the contagious, hierarchical

and related forms have been modelled for a

wide variety of diseases in different historical

and geographical settings; the classic studies

of Pyle (1969) on cholera in the nineteenth-

century USA and Cliff, Haggett, Ord and

Versey (1981) on measles in twentieth-century

Iceland are illustrative of the work undertaken.

Mathematical models of epidemic diffusion

processes can be divided into two broad types.

Intime series modelsthe past record of a disease

in a regional system is used to model its future

behaviour. Inprocess-based modelsthe person-

to-person transmission of an infectious agent

is simulated according to the parameters

of the disease and the population at risk.

Cliff, Haggett and Smallman-Raynor (1993,

pp. 359–410) provide a review of the principal

categories of model, along with a summary of

their relative merits as tools for epidemic fore-

casting. The insights offered by such model-

ling approaches are increasingly being used

in the monitoring and control of vaccine-

preventable diseases, with the prospect of the

construction of global early warning systems

for the transmission ofpandemicevents.msr

Suggested reading

Cliff, Haggett, Ord and Versey (1981); Pyle

(1979).

Disneyfication A process through which a

placebecomes marketed primarily as a tourist

destination, through standardizedlandscape

symbolization. The term derives from the

Walt Disney theme parks that originated in

California in 1955. Disneyland offered highly

organizedspacewith themed areas, united

by the central ‘Main Street’ (Avila, 2004). It

celebrates order, cleanliness and predictability

as part of the tourist-in-playground experience

(Sorkin, 1992a; Avila, 2004). Sorkin (1992a,

pp. 216–17) argues that Disney spaces cele-

brate travel and consumerism in a simulated

experience and landscape that mimics reality,

but is never quite real. The term ‘Disneyfication’

suggests a critique of this commodification

ofplace. dgm

Suggested reading

Warren (1994).

distance decay The attenuation of a pattern

or process with distance from a central point.

Gregory / The Dictionary of Human Geography 9781405132879_4_D Final Proof page 168 1.4.2009 3:15pm

DISEASE, DIFFUSION OF