Disease
• If we had a Morgan Freeman moment
could they all be stopped today?
Do you agree?
• https://www.ted.com/talks/shereen_el_feki
_how_to_fight_an_epidemic_of_bad_laws
Spread of disease
Objectives
1. Explain how the geographic concepts of
diffusion by relocation and by expansion apply to
the spread of diseases
2. Examine the application of the concept of
barriers in attempts to limit the spread of
diseases.
3. Describe the factors that have enabled
reduction in incidence of a disease
‘The greatest threat to our species is not global warming, warfare
or poverty – the greatest threat is drug-resistant bacteria’
MEDCs at greatest risk from
certain diseases.. Don’t make
that mistake!
• People in MEDCs have compromised
immune systems because of over-use of
certain antibiotics both in the
community and the food chain
How are diseases spread?
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Crowded working and living conditions
Inadequate sanitation
Unclean water supplies
Inadequate nutrition
Inadequate income  no medical help, no resources
(e.g. soap/household cleaners, mosquito
nets/repellent, antiseptic creams etc)
Long working hours
Inaccessible health care
Exposure to health risks at work as legislation not
enforced
Inadequate education e.g. AIDS sufferers not
understanding the concept of safe sex
Complete the
worksheet as
we go through
the next few
slides
•The spread of disease
into new locations –
when incidences of
diseases spread out
from an initial source.
•The frictional effect
of distance (i.e.
distance decay) 
areas closer to the
source are more likely
to be affected by it;
those further away less
likely to be affected
but might get affected
at a later date.
Incidence of disease X
Disease diffusion
Distance from source of disease
Types of diffusion
1. Expansion diffusion – including
contagious diffusion, hierarchical
diffusion and network diffusion
2. Relocation diffusion
3. Mixed diffusion
Expansion diffusion
Occurs when the expanding disease has a source and
diffuses outwards into new areas (it is the disease
that moves not the people - therefore the disease
remains at the source and often becomes more
intense).
Contagious diffusion
• The spread of an
infectious disease,
through the direct
contact of individuals
with those infected.
• Disease spreads out in
several directions from
source affecting most
individuals who come
into contact (even if do
not show symptoms)
Hierarchical diffusion
• Occurs when a phenomenon
spreads through an ordered
sequence of classes or
places, e.g. city  large
urban area  small urban
area. Or, within socially
structured populations,
innovations may be adopted
first on the upper level of
the social hierarchy and then
trickle down to the lower
levels.
• Channels of diffusion among
people or groups that are
more susceptible to the
disease - disease by passes
individuals or groups that do
not share this vulnerability
Network diffusion
• Occurs when a disease
spreads via
transportation and
social networks
• E.g. the spread of HIV
in Southern Africa along
transport routes, or the
spread of chicken pox in
schools/playgroups
Relocation diffusion
When the spreading
disease moves into
new areas, leaving
behind its origin or
source of the
disease e.g. a
person infected
with HIV moving
into a new location
Mixed diffusion
A combination of contagious diffusion and
hierarchical diffusion. AIDS is a
prominent example in modern day society
of a mixed diffusion disease, often
spreading along the hierarchal, network,
and contagious diffusion patterns.
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Disease diffusion is over simplified
• Diffusion disease looks like it goes
from one person to another. This is
only true in DIRECTLY
TRANSMITTED DISEASES
• Water borne and vector borne
diseases are slightly different (we
will come back to this later)
Barriers to stop the spread of
disease?
1. Think of ways that stop the spread of
diseases
2. For each way explain how it can and can’t
contain the disease (if applicable)
3. Can these ‘barriers’ be categorised?
Use Encephalitis in India 2012 as an example
Barriers to stop the spread of
disease?
• Natural?
• Mountains
• Water bodies –
increase
• Water bodies –
decrease
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Human?
Political boundaries
Economic boundaries
Social boundaries
Forced boundary –
imprisonment,
quarantine
Factors that have hindered reduction in
incidence of disease.. India?
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Social stigma e.g. AIDs ‘gay disease’
Social stigma e.g. leprosy due to deformaties
Education e.g. AIDs and denial in Sub-Saharan Africa
Multiple use of water source e.g. washing, cooking, sewerage,
garbage  diarrhoea
Over use of pesticides  resistance and build up in food chain
e.g. DDT
Medication side affects e.g. Malaria and liver failure
Cost e.g. TB vaccinations
Food source e.g. stagnant water in rice padi fields
Globalisation
– Increased air travel
– Risk of disease due to change in culture
– PANDEMIC VIDEO
The Pandemic Risk Index
• Pandemic disease: a disease epidemic
over a wide geographic area and
affecting a large proportion of the
population, e.g. pandemic influenza
(H1N1)
Tasks:
• Read the worksheet about the PRI
• Do you think areas of a high risk
pandemic are more likely to be found in
an HIC or an LIC? Why?
The Pandemic Risk Index
• Question: Do you think areas of a high risk
pandemic are more likely to be found in an HIC
or an LIC? Why?
• Answer: equally likely in both but for different
reasons
• LICs – usually, disease spreads easily and is
hard to contain, owing to poor medical services
and infrastructure.
• HICs – quite often there are large movements
of people through international air travel (more
globally connected) and therefore a focus for
disease transmission
Mexico – the source area for the H1N1 pandemic (2009 – 2010)
H1N1 was first reported in April 2009 – 9 countries; 148 cases, 8 deaths
One month later – May 2009 – 48 countries; 13,398 cases, 95 deaths
H1N1 – exam questions
Study the 4 maps (fig 10.18) – p.276 IB
Geography course companion
1. Describe the diffusion of the H1N1
(swine flu) virus in 2009. (3 marks)
2.Name the type of disease diffusion
indicated by the maps. Explain your
answer. (5 marks)
http://maps.google.com/maps/ms?ie=UTF8&oe=UTF8&msa=0&msid=106484775090296685271.0004681a37b713f6b5950
Exam question
• It is claimed that “the barriers to
diffusion are more difficult to identify
and define for diseases of affluence
than they are for diseases of poverty”.
Critically evaluate this statement. (10
marks)
• Use p.450-454 of Planet Geography to
help you answer this question.
The Geography of Food and Health – part 3; disease
Spread of disease
1.
Explain how the geographic concepts of
diffusion by relocation and by expansion apply to
the spread of diseases
2. Examine the application of the concept of
barriers in attempts to limit the spread of
diseases.
3. Describe the factors that have enabled
reduction in incidence of a disease
Describe the factors that have enabled
reduction in incidence of a disease
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Disease – Leprosy
Information – World Health Organisation
information sheet on leprosy
Make notes to answer the above question under the
following subheadings:
What is leprosy?
How is it transmitted?
What has been done to try to reduce the incidence
of leprosy?
How effective have these attempts been? Give
incidence of leprosy stats for before/after
Homework
Read the IB Geography course companion case studies for Geography of
Food and Health and answer the questions:
1. What is a superbug?
2. What is the link between agro-industrialisation and emerging/reemerging diseases? Give examples.
3. Can you think of any different cultural norms that may increase the
likelihood of contracting disease?
4. Can you think of any different cultural norms that may decrease the
likelihood of contracting disease?
Cholera in Haiti:
1. What kind of disease diffusion did Haiti experience?
2. Why was cholera such a big problem in Haiti, given that it is a disease
that can be treated?
3. What measures were taken to try to reduce the vulnerability of the
Haitian people?
Disease diffusion and
barriers to diffusion
Tasks:
1. Read p.447-449 of Planet Geography
2. Briefly explain how leprosy is transmitted and explain what
type of disease diffusion you think it is. Justify your answer.
3. What are the barriers to diffusion for leprosy?
4. What are the challenges in stopping/slowing the spread of
leprosy?
5. Briefly explain how 1 water borne and 1 vector borne disease is
transmitted.
6. What are the barriers to diffusion for your chosen water
borne and vector borne disease ?
7. What are the challenges in stopping/slowing the spread of your
chosen water borne and vector borne disease?
8. Explain why the principle of ‘disease diffusion’ cannot be so
easily applied to water borne and vector borne diseases