The Spread of Disease
IB Geography II
Objective
• By the end of this lesson, students will be able
to:
– Explain how the geographic concepts of diffusion
by relocation and by expansion apply to the
spread of diseases.
– Examine the application of the concept of barriers
in attempts to limit the spread of diseases.
– Describe the factors that have enabled reduction
in incidence of a disease.
Possible Exam Questions
• Explain how the geographic concept of
diffusion by ___________ applies to the
spread of diseases with reference to one
disease.
• Insert any diffusion type in blank space.
Opening Activity: Video Analysis
• Catch it, Bin it, Kill It:
http://www.youtube.com/watch?v=TcauOxev
K0g&feature=player_embedded
• Coughs & Sneezes 1945:
http://www.youtube.com/watch?v=tomNghO
NyNM&feature=player_embedded
Background on the Spread of Disease
• Infectious diseases don’t stay put. They
tend to move and spread.
• Diseases are more mobile than
previously, because we are more mobile
than before, and we carry diseases with
us.
Pandemic Risk Index
• A pandemic is a disease which has spread to
affect a very large area, either several continents
or possibly most of the globe.
• The Pandemic Risk Index takes the following into
account:
– The risk of a particular disease emerging in a country
– The risk of disease spreading to and within one
country
– The capacity of a country to contain the disease
Disease Diffusion
• Refers to the spread of a disease into new
locations
Frictional Effect of Distance (Distance
Decay)
• Suggests that areas that
are closer to the source (of
disease) are more likely to
be affected by it, whereas
areas further away from
the source are less likely to
be affected and/or will be
affected at a later date.
Barriers to Diffusion
• Some physical features act as a barrier towards
diffusion, including:
– Mountains
– Bodies of water
• Political and Economic boundaries may also limit the
spread of disease.
• Travel restrictions and screening of travelers can
form ‘human’ barriers.
• Public health advice can also help in some cases.
Types of Diffusion
•
•
•
•
•
•
Expansion diffusion
Relocation diffusion
Contagious diffusion
Hierarchal diffusion
Network diffusion
Mixed Diffusion
• Note: a Disease can spread with a
combination of above types
Expansion Diffusion
• Occurs when the
expanding disease
has a source and
diffuses outwards
into new areas
Example of Expansion Diffusion
• 1918 Spanish Flu
killed an estimated
40 million people
worldwide within just
a few months
Relocation Diffusion
• Occurs when the spreading disease moves
into new areas, leaving behind its origin or
source of the disease.
Example of Relocation Diffusion
• for example a person infected with HIV
moving into a new location.
Contagious Diffusion
• The spread of
an infectious
disease
through the
direct contact
of individuals
with those
infected.
Example of Contagious Diffusion
• The common cold:
– Ivan gets a cold. In the next few days those who sit
near him in class get the same cold from him
sneezing near them or touching desks, etc. Those
people can then get the same cold and pass it to
people sitting near them.
Hierarchal Diffusion
• Occurs when a
phenomenon spreads
through an ordered
sequence of classes or
places, for example
from cities to large
urban areas to small
urban areas.
Example of Hierarchal Diffusion
• The H1N1 Virus and other diseases.
• H1N1 started in Mexico City, but first saw
prevalence in other large cities (LA, NYC,
Chicago) before seeing a presence in smaller
cities or rural towns.
Network Diffusion
• Occurs when a
disease spreads via
transportation
networks.
• the spread of HIV in
southern Africa along
transport routes.
Another example of Network
Diffusion
• There are some cases of malaria in the US
every year for example, and most of those are
close to airports. Mosquitoes survive in the
plane just long enough to bite someone when
they leave.
Mixed Diffusion
• Usually a combination
of contagious
diffusion and
hierarchal diffusion
• Or a combination of at
least 2 other diffusion
types
Swine Flu Activity
Swine Flu
• Also known as 2009 H1N1 type A influenza, is a
human disease.
• The disease originally was nicknamed swine flu
because the virus that causes the disease originally
jumped to humans from the live pigs in which it
evolved.
• The 2009 "swine flu" outbreak was different. It was
caused by a new swine flu virus that has changed in
ways that allow it to spread from person to person -among people who haven't had any contact with
pigs.
H1N1 (Swine Flu)
• Researchers accurately plotted swine flu’s
course around the world by tracking air
travel.
• Between March and April 2009, more than
2 million people flew from Mexico to more
than 1000 cities in 164 countries.
• 4/5 of the people to cities in the US.
• http://thelede.blogs.nytimes.com/2009/07
/29/a-new-airport-ritual-swine-fluscreening/
Study the 4 maps on handout
• Describe the diffusion of the H1N1 (swine flu)
virus in 2009.
• Name the type(s) of disease diffusion
indicated by the maps. What evidence proves
it?
• What are reasons for the pattern you see?
Reduction in Incidence of Diseases
• Public health campaigns have been used for
various diseases over the years.
• There have been a range of recent scares over
possible pandemics.
• In recent years, there have been hysterical
headlines warning of mass deaths from
various diseases.
Health Screenings at Airports
• In 2009, a new
outbreak of Avian Flu
was reported in China.
• At airports, they
screen passengers by
taking their
temperature before
allowing them on the
plane.
Trends in Public Health Campaigns
• Watch this slideshow from BBC to see how
countries have tried to reduce the incidence
of disease.
• How have the messages seen changed over
time? How have they remained the same?
• How does gender play a role in reaching the
target audience in many of these ads?
http://www.bbc.co.uk/news/health-10913218