disease diffusion

• outline disease diffusion

  • the spread of a disease from the origin to a new location
  • spread from an infected to non-infected person
  • diseases spread easier than previously due to globalisation
  • transport systems spread disease on a national and international scale
• types of spatial diffusion

  1. expansion
  2. relocation
  3. contagious
  4. hierarchical

  diseases can spread by more than one type of spatial diffusion
• outline expansion - types of diffusion

  • spreads out from the origin in all directions
  • diffuses outwards into new areas
  • disease often enhances in the place of origin
  • example = 1918 Spanish flu killed 40 million within a few months
• outline relocation - types of diffusion

  • infection spreads to a new area and leaves its place of origin
  • disease dies out or is mitigated against which reduces spread in the previous area
  • example: HIV spread in Southern Africa along lorry routes when drivers had sex with sex workers
• outline contagious - types of diffusion

  • infection spreads through direct contact of the infected person with a non-infected person
  • strongly influenced by distance = closer areas at higher risk than remote areas
  • spread is outwards from origin
  • example: the common cold spreads from one person to another
• outline hierarchy - types of diffusion

  • infection spreads downwards through a system = an ordered sequence of places
  • large city to smaller town to a village
  • facilitated by transport
  • example: HIV in USA originated in san Francisco then LA then to smaller towns