1. The Spread of Disease
IB Geography II

2. 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.

3. 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.

5. Opening Activity: Video Analysis
Catch it, Bin it, Kill It:
Coughs & Sneezes 1945:

6. 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.

7. 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

10. Disease Diffusion
Refers to the spread of a disease into new locations

11. 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.

12. 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.

13. 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

14. Expansion Diffusion
Occurs when the expanding disease has a source and diffuses outwards into new areas

15. Example of Expansion Diffusion
1918 Spanish Flu killed an estimated 40 million people worldwide within just a few months

16. Relocation Diffusion
Occurs when the spreading disease moves into new areas, leaving behind its origin or source of the disease.

17. Example of Relocation Diffusion
for example a person infected with HIV moving into a new location.

18. Contagious Diffusion
The spread of an infectious disease through the direct contact of individuals with those infected.

19. 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.

20. 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.

21. 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.

22. Network Diffusion
Occurs when a disease spreads via transportation networks.
the spread of HIV in southern Africa along transport routes.

23. 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.

24. Mixed Diffusion
Usually a combination of contagious diffusion and hierarchal diffusion
Or a combination of at least 2 other diffusion types

25. Swine Flu Activity

26. 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.

28. 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.

29. 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?

30. 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.

31. 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.

32. 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?