1a.a) Classification of diseases
Infectious
• Diseases spread by pathogens
• Most can be spread person to person, but some are non-contagious like
malaria which is vector-borne
Non-infectious
• Non- communicable and occur due to genetic inheritance and lifestyle
choices
• Main cause of death in HICs but are also becoming more common in LICs
from development
Communicable
• Infectious diseases spread from host to host.
Non-communicable
• Known as chronic illnesses that occur from; environmental,
physiological, genetic and behavioural factors (e.g. cancer)
Contagious
• An infectious disease, easily spread by direct or indirect contact (e.g.
Ebola)
• Have been the main cause of death in history but the HICs now have
vaccinations
Non-contagious
• Spread only by vectors (e.g. Malaria)
Epidemic
• Disease outbreak that spreads quickly in through population of
geographical area
• The measles outbreak in the UK
Pandemic
• Disease outbreak spreading worldwide
• Current pandemic of HIV/AIDS
endemic
• Disease that permanently exists in a geographical area or population
• Sleeping sickness in sub-Saharan Africa
,1a.b) Global distribution of disease
,1a.c) Disease diffusion
Disease diffusion - disease spreading outwards from origin
Physical barriers Socio-economic
Distance Political borders
• Probability of disease • Close borders
spreading to an area is • Quarantine
proportional to distance • Check international
from source movement of
Climate carriers
Health education
• Antarctica and deserts;
Imposing curfews
no population
• Different temperatures • Limit contact
for vectors between people
Mountains, seas and desert • Neighbourhood effect
• Slow down & halt • Telling to wash
diffusion hands
Mass vaccination
• Expensive to cross for
LICs • Precautions e.g.
• Traps disease in specific facemasks
area; globalisation ruins
it.
Torsten Hagerstrand model
1. Neighbourhood effect - probability of contact between a carrier and a
non-carrier is determined by how many people live in a 5x5km square and
the distance between them (population density). Closer proximity means
higher chance of contracting disease.
2. After a slower beginning the rate of infection rapidly increases until
eventually levelling out as most of population is already infected
3. Diffusion may be interrupted by physical barriers, which make the model
probabilistic rather than deterministic
, Expansion diffusion Relocation diffusion
Diseases leaves area of
Disease spreads origin and moves to a new
outwards but carriers place
stay infected E.g. cholera moving from
E.g. TB Nepal to Haiti.
Contagious diffusion Hierarchical diffusion
Spreads through an ordered
Spread through direct sequence of places, city
contact with a carrier. centres to small towns.
E.g. Ebola epidemic in Can be channelled along
west Africa 2014-2015 transport networks E.g.
Covid-19
Infectious
• Diseases spread by pathogens
• Most can be spread person to person, but some are non-contagious like
malaria which is vector-borne
Non-infectious
• Non- communicable and occur due to genetic inheritance and lifestyle
choices
• Main cause of death in HICs but are also becoming more common in LICs
from development
Communicable
• Infectious diseases spread from host to host.
Non-communicable
• Known as chronic illnesses that occur from; environmental,
physiological, genetic and behavioural factors (e.g. cancer)
Contagious
• An infectious disease, easily spread by direct or indirect contact (e.g.
Ebola)
• Have been the main cause of death in history but the HICs now have
vaccinations
Non-contagious
• Spread only by vectors (e.g. Malaria)
Epidemic
• Disease outbreak that spreads quickly in through population of
geographical area
• The measles outbreak in the UK
Pandemic
• Disease outbreak spreading worldwide
• Current pandemic of HIV/AIDS
endemic
• Disease that permanently exists in a geographical area or population
• Sleeping sickness in sub-Saharan Africa
,1a.b) Global distribution of disease
,1a.c) Disease diffusion
Disease diffusion - disease spreading outwards from origin
Physical barriers Socio-economic
Distance Political borders
• Probability of disease • Close borders
spreading to an area is • Quarantine
proportional to distance • Check international
from source movement of
Climate carriers
Health education
• Antarctica and deserts;
Imposing curfews
no population
• Different temperatures • Limit contact
for vectors between people
Mountains, seas and desert • Neighbourhood effect
• Slow down & halt • Telling to wash
diffusion hands
Mass vaccination
• Expensive to cross for
LICs • Precautions e.g.
• Traps disease in specific facemasks
area; globalisation ruins
it.
Torsten Hagerstrand model
1. Neighbourhood effect - probability of contact between a carrier and a
non-carrier is determined by how many people live in a 5x5km square and
the distance between them (population density). Closer proximity means
higher chance of contracting disease.
2. After a slower beginning the rate of infection rapidly increases until
eventually levelling out as most of population is already infected
3. Diffusion may be interrupted by physical barriers, which make the model
probabilistic rather than deterministic
, Expansion diffusion Relocation diffusion
Diseases leaves area of
Disease spreads origin and moves to a new
outwards but carriers place
stay infected E.g. cholera moving from
E.g. TB Nepal to Haiti.
Contagious diffusion Hierarchical diffusion
Spreads through an ordered
Spread through direct sequence of places, city
contact with a carrier. centres to small towns.
E.g. Ebola epidemic in Can be channelled along
west Africa 2014-2015 transport networks E.g.
Covid-19
