- What are the global patterns of disease and can factors be identified that determine these?
Patterns of disease
Classification
Infectious : A disease spread by parasites, bacteria, viruses and fungi
Non infectious : A non-communicable disease due to age or genetic defects
Communicable : An infectious disease that spreads from host to host
Non- communicable : A disease that cannot be spread between people
Contagious : A disease spread by contact or indirect contact
Non contagious : A disease not spread by contact or indirect contact between people
Epidemic : An outbreak of disease that spreads quickly and affects many people not in a defined geographical area
Pandemic : An epidemic which spreads worldwide Eg. Spanish Flu
Endemic : A disease that exists permanently in a geographical area or human group
HIV
Malaria
CVD
Diabetes
TB
Disease diffusion and spread
Physical barriers to diffusion
Stages of diffusion
Socio-economic barriers to diffusion
Hägerstrand model
Types of diffusion
Hierarchal : Through an ordered sequence of places, large centres to smaller isolated centres Eg. Spanish Flu
Relocation : Disease leaved area of origin and moves into
new areas Eg. Cholera epidemic in Nepal --> Haiti
Expansion : A disease has a source and expands outwards into new areas while the carriers in the source area remain infected Eg TB
Contagious : Spread of disease through direct contact with a carrier. Strongly influenced by distance
Physical factors and prevalence
Zoonotic diseases
Seasonal variations (Monsoons)
Physical factors
Temperature
Relief
Precipitation
Water sources
Ringworm
Natural hazard
Mitigation strategies
Human factors
Impact of disease
Environmental factors
Climate
Sanitation
Water supply
Food
Population density
Access to clean water
Immunisation programmes
National scale
International scale
Infectious but non-contagious tropical disease
Concentrated in Africa, Latin America, South Asia : equatorial regions
Malarial parasite is transmitted to humans by Anopheles mosquitoes which thrive in warm humid environments
Infectious highly contagious disease associated with poverty and overcrowded living conditions
In 2013 there were 9 million cases worldwide and 1.5 million deaths
Africa has the highest number of deaths, with a large proportion among HIV/AIDS sufferers making them more susceptible due to weak immunity
Infectious contagious disease
Spread by human bodily fluids such as blood and semen
Sub-Saharan Africa with South Africa and Nigeria having the largest number of cases
25% of Lesotho and Swaziland carry the disease
In 2015 35 million people infected
Age causes incidence to rise
Russia due to alcoholism (cold climate/ culture)
Sub Saharan Africa and Arabian Peninsula
17 Million deaths a year with 80% occurring in low- and middle income countries
Premature death from lifestyle, tobacco consumption, unhealthy diet and physical inactivity
Non - communicable disease caused by deficiency of insulin, a hormone secreted by the pancreas
Afflicts nearly 250 million people a year and is responsible for 4 million deaths
Type 1 : In childhood as its genetic
Type 2 : In adults and is often linked to obesity, poor diet and physical inactivity
- Slow rate of diffusion as few people have it
- Infected rate increases rapidly as the disease is passed on
- Most people have had the disease so there are less people to diffuse to
- Most of the susceptible population have been infected
Deserts
Seas/ oceans
Mountain ranges
Distance
Climate
Political border checks
Imposing curfews to limit contact between people (Covid)
Mass vaccination programmes to protect populations against disease
Cancelling public events
Wearing face-masks in public
The probability of a contagious disease spreading to an area is inversely proportional to distance from its source
Their is a neighbourhood effect in diffusion
The probability of contact between a carrier and a non-carrier is determined by the umber of people living in each 5 X 5 KM grid square and their distance apart
People living in closer proximity to carriers have a greater probability of contracting a disease than those located further away
Creates aquatic habitats such as ponds or stagnant pools which allow disease vectors and insects to flourish
Water borne diseases - Cholera
Flooding can cause the spread of disease
Determines the rates of vector development and behaviour as well as viral replication
Transmission of the flu virus is most efficient at lower temps
Water and wetter conditions favoured the growth and spread of mosquitoes carrying sub-tropical diseases -- > WNV
Altitude causes abrupt changes in climate and disease habitats
In Ethiopia malaria is concentrated in humid lowlands but is largely absent in cooler highlands
High water stress causes people to drink dirty disease filled water
Low water stress : Can afford to move and drink safe water
April - September
Warm moist air from the SW Indian Ocean blows towards India/ Bangladesh. Meeting cold dry air from North ITCZ
Causes a humid climate and torrential rainfall
Linked to malaria as bodies of standing water are created by rain
Climate change
WNV
Climate change
Efforts to limit spread
Reduce exposure
Pesticides and wearing mosquito nets
Reduce risk through organ transplant
Gloves or protective clothing when treating sick animals or when slaughtering
Reducing mosquito transmission
No vaccine available for humans
Vaccines have been developed for horses
Intervention fluids
Hospitalisation
Effects
People over age of 50 or with certain medical conditions are more at risk
Headaches, paralysis, vision loss, convulsions
1/150 severe illness affecting the CNS
1/5 develop a fever, body ache, joint pain
8/10 asymptomatic
Spread through contact with other infected animals, their blood, organ transplant and breast milk (No human - human direct yet )
From bites of infected mosquitoes who get it from infected birds : virus goes into the salivary glands
Zoonotic disease - Infectious contagious
Increased risk of human exposure to WNV
Warmer temperatures accelerate mosquito development, biting rates and the incubation of the disease within a mosquito
Timing of bird migration = long range virus movement
Direct contact with main reservoirs passed on through close contact with infected person, infected animal and object
12,500 new cases annually
Lyme disease
Tick bite with reservoirs in ticks, rodents, deer, sheep and small mammals
Given to humans through the bite of a infected lxodes ricinus tick
Common in Scottish Highlands ( In Bra-ken grass)
2,000-3,00 new cases in England
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