Disease diffusion

• Expansion diffusion


  The disease has a source and spreads to new areas while source area remain infected.
• Relocation diffusion


  The disease leaves the area of origin and moves into new areas.
• Contagious diffusion


  The spread is though direct contact with a carrier.
• Hierarchical diffusion


  disease spreads through a structured sequence of locations e.g from large, well-connected centres to smaller, more isolated centres.
• Disease diffusion


  process by which a disease spreads outwards beyond it’s geographical source.
• Hägerstrand’s diffusion model

  Explains how new ideas or innovations spread through a population over time.

  Considering factors like individual characteristics and geographic context.

  Applies to contagious diffusion of disease.
• Neighbourhood effect


  The probability of contact between those infected and those not infected; the influence of distance decay.
• Hägerstrand’s diffusion model; number of infected people.


  represented by an S-shaped curve over the duration of time.
• Hägerstand’s model; primary stage.


  Strong contrast in disease incidence between the area of outbreak and remote areas.
• Hägerstrand's model; Diffusion stage


  New centres of disease outbreak occur far from the source, reducing spatial contrasts of the primary stage.
• Hägerstrand's model; condensing stage


  Amount of new cases is more equal in all locations, regardless of distance from the source.
• Hägerstrand's model; saturation stage


  Diffusion decelerates as spread of disease reaches its peak.
• Physical barriers


  Distance, mountains, sea, deserts and climate change.
• Socio-economic barriers

  Political border checks, imposition of curfews or quarantining.

  Implemented by international or national governments.