EQ2: What are the causes of health risks? Aims: To understand how models can help in the understanding of health risk causes and patterns
How diseases spread through a population has long been studied by both epidemiologists and geographers. The last section you studied looked at geographical pathways and patterns and how certain diseases spread. This section looks at spatial patterns as well as temporal ones.
Remember that a model concentrates only on major characteristics and processes. It makes understanding easier at the start of the learning process. However, once clear about the framework of the process or a situation, it is then not too difficult to understand the detail. Read the overview in PA pages 360-361 (SMALL TEXT) and then visit http://www.makingthemodernworld.org.uk/learning_modules/geography/05.TU.01/?section=1 Make sure that you can draw and explain each model and explain both its positive and negative points.
<ul><li>Diffusion Model </li></ul><ul><li>Four types recognised by Hagerstrand (in the 1950s): </li></ul><ul><li>Expansion </li></ul><ul><li>Contagious </li></ul><ul><li>Relocation </li></ul><ul><li>Hierarchical </li></ul>
4 Hamer-Sopel models examine the spread of disease in relation to fertility, mortality and migration. The Models use an island to illustrate the points.
Kilbourne saw influenza spread out in waves with a higher incidence in winter than in summer. Magnitude of waves decreases over time and strain dies out. The virus has the ability to change its antigens so that the body’s defence mechanism does not recognise it. This means that a new strain may begin with a wave pattern similar to the original strain.
The core-periphery model is a general model that geographers use and can be applied to a number of scenarios including the spread of disease. With its larger and more dense population, the core has much greater mixing rates amongst the population than the sparsely populated periphery. Sometimes the focus or source of an epidemic is in the periphery. The infection may then travel from the periphery to the core before being spread to other peripheral areas.
Bartlett’s model looks at the minimum number of people needed in any population to support an endemic disease.
You need to be able to discuss the models in relation to various diseases. Go back to your report of 2.3 and apply the models to the diseases that you chose.