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=TcauOxevK0g&feature=player_embedded

• Coughs & Sneezes 1945: http://www.youtube.com/watch?v=tomNghONyNM&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-flu-screening/

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