1.A - how do diseases spread to new areas? Flashcards
how do diseases spread?
- migration and travel (time space compression, ACs/urban areas more affected)
- poor living conditions/crowding
- lack of education
- climate
- proximity to outbreak
- animals
what seems to stop disease spreading?
- oceans/physical barriers
- lockdowns/quarantines
- vaccines
- altitude/low temperatures
what facilitates disease spreading?
- animals/vectors
- direct transmission - sneezing/bodily fluids
- water/stagnant water
- temperature/climate change
what model is used to show the spread of disease?
Hagerstrand model
what shape is the Hagerstrand model and why?
- S shaped curve
- the number of people infected by an epidemic approximates an S shaped or logistic curve over time
- after a slow beginning, the number infected accelerates rapidly until eventually levelling out, as most of the susceptible population have been infected
how does the Hagerstrand model graph change between different countries and why?
- the progress and diffusion of a disease may be interrupted by physical barriers
what are the 4 stages of the hagerstrand model?
- PRIMARY STAGE - outbreak is slow as it spreads from one fixed point. typically lasts for months. eventually disease reaches enough people and spreads exponentially
- EXPANSION STAGE - rapid growth occurs due to contagious diffusion of populations. rate of infection rapidly increases, accelerated by travel, poor education, sanitation etc.
- CONDENSATION STAGE - disease spread slows as populations become immune/already infected/barriers to diffusion take over. we become educated/vaccination/quarantined
- SATURATION STAGE - disease spread stops. no new cases. everyones got it or everyones vaccinated.
what is stage one of the Hagerstrand model?
PRIMARY STAGE - outbreak is slow as it spreads from one fixed point. typically lasts for months. eventually disease reaches enough people and spreads exponentially
what is stage two of the Hagerstrand model?
EXPANSION STAGE - rapid growth occurs due to contagious diffusion of populations. rate of infection rapidly increases, accelerated by travel, poor education, sanitation etc.
what is stage three of the Hagerstrand model?
CONDENSATION STAGE - disease spread slows as populations become immune/already infected/barriers to diffusion take over. we become educated/vaccination/quarantined
what is stage four of the Hagerstrand model?
SATURATION STAGE - disease spread stops. no new cases. everyones got it or everyones vaccinated.
what is the neighbourhood effect?
- people living in proximity to carriers have a greater probability of contracting a disease than those located further away
- close proximity to outbreak = ↑ likelihood of contracting disease = contagious diffusion
what human factors could affect Hagerstrand’s model of how disease spread?
- population growth
- urbanisation brings with it the problems of housing, sanitation, pollution etc.
- migration/travel
- hunting and pasture practices
how does a disease reach the “saturation” phase?
- the number infected eventually levels off as most of the susceptible population have been infected
what are the 4 main types of disease diffusion?
- expansion diffusion
- relocation diffusion
- hierarchial diffusion
- contagious diffusion
what is expansion diffusion?
- a disease has a source and spreads outwards into new areas
- meanwhile, carriers in the source area remain infected
- outbreak of TB is an example of expansion diffusion
- no transport/barriers involved
what is relocation diffusion?
- occurs when a disease leaves the area of origin and moves into new areas
- the cholera epidemic in Haiti in 2010, which killed 7000 people, illustrates this process
- the disease, which originated in Nepal, was brought to Haiti by international air workers flown in to tackle the earthquake disaster of that year
what is hierarchial diffusion?
- a disease spreads through an ordered sequence of places, usually from the largest more isolated centres
- diffusion is also channelled along road, rail and air transport networks which facilitate contact between carriers and a susceptible population
- in 2009 the H1N1 flu virus became a pandemic via international flight routes and airports
what is contagious diffusion?
fast expansion
what is network diffusion?
- network diffusion occurs when a disease spreads via transportation and social networks.
what are the key barriers to diffusion?
- mass vaccination
- PHYSICAL BARRIERS:
- distance
- mountain ranges, seas, oceans, deserts and climate (e.g. malaria/flu season) - education policies e.g. lockdown
- political borders (control flows of people - NE/AU in COVID)
- distance from source - isolation
what helps the rate of diffusion?
- proximity
- crowded areas/city
- going out if infected
- not having a vaccine
how is HIV diffused?
POVERTY
- lack of education
- traditional belief systems/taboos
- lack of access to ATVs
- poor nutrition, sanitation, water shortage
- prostitution
- marginalised women/dominance of males over females
