The big idea: The geography of disease asks how a disease spreads from place to place — its diffusion — and what speeds it up or stops it.
A disease spreads when there is a source, a route of transmission, and people who can catch it. Geographers study the physical, human, economic, social and political factors that decide how fast and how far it diffuses, and the barriers that slow it down.
Key terms
- Diffusion — the way a disease spreads outward across space and through a population over time.
- Expansion diffusion — the disease spreads outward from a source while staying there too (it grows, like ripples), e.g. cholera through a crowded settlement.
- Relocation diffusion — infected people carry the disease to a new area as they move (the source area may recover), e.g. a traveller flying with dengue.
- Vector-borne disease — spread by an organism such as a mosquito (e.g. malaria, dengue).
- Water-borne disease — spread through contaminated water (e.g. cholera, typhoid).
- Barrier — anything that slows or blocks diffusion (mountains, quarantine, vaccination, clean water).
Two types of diffusion: Expansion = the disease stays and spreads outward (it ripples through a place).
Relocation = an infected person moves and takes it elsewhere (the original area can recover).
Long-distance air travel is the classic relocation route — it lets a disease jump across the world in a day.
How this is tested: Paper 2 / Paper 1 Option F opens with a data-response on a disease graph — a cholera outbreak curve, a dengue-by-age graph, or a mosquito-net bar graph. You Estimate or State a value (a peak, an average, a category) or Identify a trend or a likely cause. Always read the correct axis and quote the units.
| Week | Reported cases | What is happening |
|---|---|---|
| 1 (Oct) | 20 | First cases near a contaminated shallow well |
| 3 | 180 | Expansion diffusion through the crowded settlement |
| 5 | 520 | Peak as floodwater mixes sewage with drinking water |
| 7 | 710 | Outbreak peak — clinics overwhelmed |
| 9 | 240 | Cases fall as chlorinated water + oral rehydration arrive |
| 12 | 60 | Outbreak nearly controlled |
| 16 (Feb) | 330 | Resurgence — heavy rains and flooding return |
Expansion vs relocation, and the barriers
- Expansion diffusion drives the early climb — cases ripple out from the first well through a dense settlement.
- Relocation diffusion would carry it further — a trader leaving the area takes cholera to the next town.
- Physical barrier — a dry season or a river/mountain that cuts off contact slows the spread.
- Human/political barriers — chlorinating water, oral rehydration, health education and quarantine flatten the curve.
- Why it resurges — when heavy rain and flooding return (week 16), the physical driver comes back and cases climb again.
Estimate = a sensible read; State = the exact value: Estimate the peak by reading the highest point off the axis (here about 710 cases in week 7). State an exact category or value the table/graph gives directly. Identify a cause = name a sensible factor that fits the trend (e.g. the resurgence follows the rains).
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Examiners want the mechanism — how a factor moves the disease from place to place. For each factor, name it, then trace the chain to more transmission or faster diffusion. A top answer names a real disease and place.
| Factor | How it speeds diffusion |
|---|---|
| Physical: warm, wet climate | Standing water and heat let mosquitoes breed fast -> more vectors -> more malaria/dengue |
| Physical: rainfall + flooding | Floods mix sewage with drinking water -> water-borne cholera/typhoid spread |
| Human: migration + air travel | Infected people relocate the disease to new areas (relocation diffusion) |
| Human: overcrowding + poor sanitation | People live close with no clean water/toilets -> fast person-to-person spread |
| Economic: poverty + weak healthcare | No money for nets, drugs, clean water or clinics -> the disease is not stopped |
| Social/political: weak governance, conflict | Health services collapse and barriers (vaccination, quarantine) fail |
Cholera in Haiti (2010) and Lusaka, Zambia: After the 2010 Haiti earthquake, cholera was relocated in by people, then spread by expansion diffusion through camps with no clean water — tens of thousands died.
In Lusaka, Zambia, cholera outbreaks return each rainy season: flooding contaminates shallow wells in crowded informal settlements. Both show physical triggers (flood/quake) working through human vulnerability (poverty, poor sanitation).
Malaria in sub-Saharan Africa: Malaria is vector-borne by the Anopheles mosquito. Across sub-Saharan Africa the warm, wet climate gives year-round breeding, while poverty limits nets, drugs and drained land — so the disease persists.
Where insecticide-treated bed nets and spraying have been scaled up (e.g. parts of Rwanda and Tanzania), child cases have fallen — a human barrier working against a physical driver.
Always name the disease: The markscheme caps you at 4-5/6 if you give no specific disease, or name a vector-borne disease when the question wants water-borne (or the reverse). Name it in your first line: Cholera is a water-borne disease...
How this is tested — the [10] essay: Option F ends with a 10-mark essay marked on markbands (Examine / To what extent). Recurring versions weigh physical vs human factors, diffusion and barriers, or economic vs other factors in disease spread.
Top band needs: accurate terms, a named disease + place, two or more developed factors, a weighing of their relative importance (often how it changes over time), and a clear conclusion. Choosing the wrong disease type for the question caps you at 4.
Markband marks: (1) Name a real disease + place and check it fits the question type (vector-borne / water-borne / economic). (2) Develop two+ factors, not a list. (3) Weigh them — which matters most, and how it changes over time / by scale. (4) End on an explicit judgement.