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3.2.1 Global Patterns of Disease
Topic Human - Disease Dilemmas
1.1 Diseases can be Classified and their
Patterns Mapped
How diseases can be classified, including infectious and non-infectious,
communicable and noncommunicable, contagious and non-contagious,
epidemic, endemic and pandemic.
Patterns of diseases, including global distributions of malaria, HIV,
tuberculosis, diabetes and cardio-vascular disease.
Disease diffusion and spread to new areas (Hägerstrand model), including
the phases of diffusion, physical and socio-economic barriers.
Disease Classification
Infectious vs Non‑infectious
Infectious diseases are caused by pathogens such as bacteria, viruses,
parasites or fungi. They may or may not be transmissible.
Non‑communicable diseases (NCDs) are long‑lasting, non‑transmissible
diseases such as cardiovascular disease, cancers, chronic respiratory
diseases and diabetes.
Communicable vs Non‑communicable
Communicable diseases spread from person to person via direct or
indirect contact.
Non‑communicable diseases do not spread between people and are linked
to lifestyle, genetics and environmental factors.
3.2.1 Global Patterns of Disease 1
, Contagious vs Non‑contagious
Contagious diseases spread easily through direct or indirect contact (e.g.
coughing, bodily fluids).
Non‑contagious infectious diseases require a specific transmission route
such as a vector (e.g. malaria via mosquitoes).
Zoonotic
Diseases transmitted from animals to humans (e.g. rabies, West Nile Virus).
Epidemic, Endemic, Pandemic
Epidemic – sudden rise in cases above expected levels.
Endemic – disease permanently present in a region.
Pandemic – epidemic spreading across multiple countries or continents.
Global Patterns of Disease
Malaria
Highest incidence in sub‑Saharan Africa (over 25,000 cases per 100,000).
Also present in Brazil and Southeast Asia.
Absent in temperate regions (Europe, North America, Australia).
Driven by strict climatic requirements: warm temperatures (22–30°C),
humidity, stagnant water, and weak healthcare systems.
HIV/AIDS
Highest death rates in Southern Africa.
Also high across sub‑Saharan Africa and parts of South/Southeast Asia.
Low in high‑income regions due to widespread access to antiretroviral
therapy.
Influenced by poverty, stigma, gender inequality, migration and weak
healthcare systems.
Tuberculosis
Highest mortality in sub‑Saharan Africa.
3.2.1 Global Patterns of Disease 2
, Also high in densely populated developing nations in Asia (India, China,
Indonesia, Philippines).
Strongly associated with malnutrition, overcrowding and poor ventilation.
Cardiovascular Disease (CVD)
Highest in Eastern Europe and Central Asia.
Also high in East Asia and the Middle East.
Lowest in Western Europe, North America and Australia.
Linked to smoking, alcohol consumption, high‑fat diets, air pollution and
limited preventative healthcare.
Diabetes
Highest prevalence in the Middle East, USA, Mexico, and Southeast Asia.
Lower in much of Africa and rural South America/Asia.
Driven by urbanisation, processed diets, sedentary lifestyles and genetic
susceptibility.
Disease Diffusion (Hägerstrand Model)
Key Concepts
Neighbourhood effect – people near carriers have a higher chance of
infection.
Distance decay – likelihood of spread decreases with distance.
S‑curve (logistic curve) – slow initial spread → rapid growth → plateau as
susceptible population declines.
Physical barriers can interrupt diffusion (mountains, oceans, climate).
Types of Diffusion
Expansion diffusion – disease spreads outward but remains at origin (e.g.
TB).
Contagious diffusion – spread through direct contact; strongest near origin
(e.g. Ebola).
3.2.1 Global Patterns of Disease 3
, Hierarchical diffusion – spreads via major population centres first (e.g. HIV
in USA, H1N1 via airports).
Relocation diffusion – disease moves to new areas via carriers (e.g.
cholera in Haiti, WNV via migratory birds).
Barriers to Diffusion
Physical geography
Public health systems
Vaccination and immunity
Cultural norms
Economic resources
Travel controls
Sanitation and hygiene
Disease surveillance
Climate and environmental limits
1.2 There is a Relationship between
Physical Factors and the Prevalence of
Disease
Global patterns of temperature, precipitation, relief and water sources and
how they affect patterns of disease.
Physical factors can influence vectors of disease such as the prevalence of
mosquitoes in warm, humid areas close to water sources.
How seasonal variations influence disease outbreaks such as periods of
drought or monsoon rains.
Climate change provides the conditions for emerging infectious diseases to
spread to new places and new hosts such as West Nile virus, tsetse fly and
tick seasons.
The conditions for zoonotic infectious diseases such as bird flu or rabies to
establish and spread from animals to humans.
3.2.1 Global Patterns of Disease 4
3.2.1 Global Patterns of Disease
Topic Human - Disease Dilemmas
1.1 Diseases can be Classified and their
Patterns Mapped
How diseases can be classified, including infectious and non-infectious,
communicable and noncommunicable, contagious and non-contagious,
epidemic, endemic and pandemic.
Patterns of diseases, including global distributions of malaria, HIV,
tuberculosis, diabetes and cardio-vascular disease.
Disease diffusion and spread to new areas (Hägerstrand model), including
the phases of diffusion, physical and socio-economic barriers.
Disease Classification
Infectious vs Non‑infectious
Infectious diseases are caused by pathogens such as bacteria, viruses,
parasites or fungi. They may or may not be transmissible.
Non‑communicable diseases (NCDs) are long‑lasting, non‑transmissible
diseases such as cardiovascular disease, cancers, chronic respiratory
diseases and diabetes.
Communicable vs Non‑communicable
Communicable diseases spread from person to person via direct or
indirect contact.
Non‑communicable diseases do not spread between people and are linked
to lifestyle, genetics and environmental factors.
3.2.1 Global Patterns of Disease 1
, Contagious vs Non‑contagious
Contagious diseases spread easily through direct or indirect contact (e.g.
coughing, bodily fluids).
Non‑contagious infectious diseases require a specific transmission route
such as a vector (e.g. malaria via mosquitoes).
Zoonotic
Diseases transmitted from animals to humans (e.g. rabies, West Nile Virus).
Epidemic, Endemic, Pandemic
Epidemic – sudden rise in cases above expected levels.
Endemic – disease permanently present in a region.
Pandemic – epidemic spreading across multiple countries or continents.
Global Patterns of Disease
Malaria
Highest incidence in sub‑Saharan Africa (over 25,000 cases per 100,000).
Also present in Brazil and Southeast Asia.
Absent in temperate regions (Europe, North America, Australia).
Driven by strict climatic requirements: warm temperatures (22–30°C),
humidity, stagnant water, and weak healthcare systems.
HIV/AIDS
Highest death rates in Southern Africa.
Also high across sub‑Saharan Africa and parts of South/Southeast Asia.
Low in high‑income regions due to widespread access to antiretroviral
therapy.
Influenced by poverty, stigma, gender inequality, migration and weak
healthcare systems.
Tuberculosis
Highest mortality in sub‑Saharan Africa.
3.2.1 Global Patterns of Disease 2
, Also high in densely populated developing nations in Asia (India, China,
Indonesia, Philippines).
Strongly associated with malnutrition, overcrowding and poor ventilation.
Cardiovascular Disease (CVD)
Highest in Eastern Europe and Central Asia.
Also high in East Asia and the Middle East.
Lowest in Western Europe, North America and Australia.
Linked to smoking, alcohol consumption, high‑fat diets, air pollution and
limited preventative healthcare.
Diabetes
Highest prevalence in the Middle East, USA, Mexico, and Southeast Asia.
Lower in much of Africa and rural South America/Asia.
Driven by urbanisation, processed diets, sedentary lifestyles and genetic
susceptibility.
Disease Diffusion (Hägerstrand Model)
Key Concepts
Neighbourhood effect – people near carriers have a higher chance of
infection.
Distance decay – likelihood of spread decreases with distance.
S‑curve (logistic curve) – slow initial spread → rapid growth → plateau as
susceptible population declines.
Physical barriers can interrupt diffusion (mountains, oceans, climate).
Types of Diffusion
Expansion diffusion – disease spreads outward but remains at origin (e.g.
TB).
Contagious diffusion – spread through direct contact; strongest near origin
(e.g. Ebola).
3.2.1 Global Patterns of Disease 3
, Hierarchical diffusion – spreads via major population centres first (e.g. HIV
in USA, H1N1 via airports).
Relocation diffusion – disease moves to new areas via carriers (e.g.
cholera in Haiti, WNV via migratory birds).
Barriers to Diffusion
Physical geography
Public health systems
Vaccination and immunity
Cultural norms
Economic resources
Travel controls
Sanitation and hygiene
Disease surveillance
Climate and environmental limits
1.2 There is a Relationship between
Physical Factors and the Prevalence of
Disease
Global patterns of temperature, precipitation, relief and water sources and
how they affect patterns of disease.
Physical factors can influence vectors of disease such as the prevalence of
mosquitoes in warm, humid areas close to water sources.
How seasonal variations influence disease outbreaks such as periods of
drought or monsoon rains.
Climate change provides the conditions for emerging infectious diseases to
spread to new places and new hosts such as West Nile virus, tsetse fly and
tick seasons.
The conditions for zoonotic infectious diseases such as bird flu or rabies to
establish and spread from animals to humans.
3.2.1 Global Patterns of Disease 4
