Factors Contributing to Diffusion (SL IB Geography)

Geographic Factors Contributing to Diffusion 

• Diffusion of disease is its spread from place to place
• The disease incidence rate is the number of new disease cases over a specific period, in relation to the overall population of an area
• Geographic factors are physical and human characteristics that affect incidence and diffusion rates 
  • Vector-borne disease transmits to humans from another vector e.g. animals like mosquitos or tics
    • These include diseases such as dengue fever, malaria and Lyme disease
  • Water-borne diseases result from poor sanitation, hygiene and the consumption of unsafe water
    • They include cholera, typhoid, diarrhoea and dysentery 

Physical 

• Warmer climates, like tropical latitudes, make it easier for vector-borne diseases to spread
  • Mosquitos thrive in warm and humid environments 
  • Climate change is likely to worsen this, as vectors may spread to areas such as southern Europe
• Heavy rainfall can cause flooding, leaving behind large areas of stagnant water
  • Vectors thrive in these stagnant water bodies e.g. mosquitos 
  • For example, water may stand near populated areas or in irrigation channels
• Natural disasters could increase dirty water
  • Flood or tsunami waters may contain sewage 
  • Earthquakes or hurricanes can damage sewage systems, allowing sewage to enter drinking water sources
• Rich biodiversity causes dilution of vector-borne diseases
  • With human-induced climate change, biodiversity will decrease
  • This will increase disease spread

Economic/political

• Less developed countries have poor sanitation and hygiene, which increases the risk of water-borne diseases 
• Education rates are also lower, with little knowledge about hygiene and disease spread 
• Less developed countries also have poorer quality healthcare, e.g vaccines
• War and conflict can result in higher disease incidence:
  • Destruction of healthcare infrastructure, like hospitals 
  • Damage to sewage pipelines, resulting in contaminated water 
  • Debris contamination in stagnant water
• Industry development may also cause diffusion:
  • Logging within tropical rainforests increases temperatures in the area
    • Heavy rainfall causes flooding of the cleared/deforested land or increases
  • Water collects in mining pits, irrigation channels and rice paddy fields, where vectors breed more efficiently 
  • Agriculture (e.g. livestock) can provide food for vectors, increasing their population

Social and cultural

• Migrants or settlers may move to an area that already has high immunity and contract vector-borne diseases
• Urbanisation causes increased unregulated development in areas where vectors thrive or where other non-human disease hosts exist
• Globalisation has meant that new non-indigenous vectors can move around the world

Demographic

• Water-borne diseases heavily impact children, causing higher mortality rates in younger people
• Vector-borne diseases like malaria heavily impact children and pregnant women 
• Malaria impacts Maternal Mortality rates
• Immunocompromised people have a higher risk of contracting malaria e.g. HIV
• Diseases impact travellers, as they haven’t been exposed to the disease and have no immunity e.g. malaria
• Lower-income groups/those in poverty are more at risk of vector and water-borne diseases
• Many developing countries lie in warmer/tropical regions, where vector-borne diseases thrive
• Poor sanitation and unsafe water increases the risk of water-borne diseases 
• Both vector-borne and water-borne diseases can impact death rates in a country

Deaths from vector-borne diseases

Socio-economic

•  In lower-income countries, people travel far to collect safe water, usually by foot
  • It may take a long time to get to the water source
  • This can mean they do not go to work, which can negatively affect the economy 
  • They may suffer physically as a result of strenuous activity
• Disease prevention programmes can be costly
  • This can include bug nets or repellants and medical fees
  • This can cause problems for lower-income countries, which already struggle with economic development 
• Children may not be able to attend school due to sickness, reducing education rates 
• The tourism industry may take a hit. Foreign travellers may be wary about entering a country e.g. the Caribbean and Latin America experienced large losses in the tourism industry after the Zika virus hit in 2015