Factors Contributing to Diffusion | SL IB Geography Revision Notes 2019

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

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

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

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

Water-borne diseases heavily impact children, causing higher mortality rates in younger people
Vector-borne diseases like malaria heavily impact children and pregnant women

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

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