Studied by 3 people
What is an infectious disease?
Spread y pathogens
Most but not all are spread person to person
What is a contagious disease?
Infectious diseases that can spread by direct contact
e.g. typhoid, Ebola
What is a communicable disease?
Spread from host to host but doesn’t require quarantine
Some are non-contagious e.g. malaria
What is a zoonotic disease?
Infectious disease that are spread from animals to humans
e.g. rabies
What is a non infectious disease?
Not communicable
Causes are genetics, lifestyle and environment
What is an endemic?
They exist permanently in a geographical area or population
e.g. sleeping sickness in Sub-Saharan Africa
What is an epidemic?
An outbreak of disease that attacks people and spreads through a population in a restricted geographical area
What is a pandemic?
An epidemic that spreads worldwide
e.g. Covid-19
What are degenerative diseases?
60% of worldwide deaths are due to ageing population and increasing unhealthy lifestyle
e.g. dementia, cancer
Also influenced by lifestyle choices such as smoking and stress
What is the distribution of malaria across the world?
Most concentrated in the tropics where there is high humidity
Tropical disease
Infectious but not contagious
Africa, Southeast Asia and Latin America
3.2 billion people are at risk in 97 countries
Transmitted by mosquitos
What is the distribution of HIV/AIDS across the world?
Infectious and contagious
Spread by bodily fluids like semen and blood
Concentrated in Sub-Saharan Africa
In 2015 35 million people were infected with HIV/AIDS
What is the distribution of TB across the world?
Tuberculosis is infectious and contagious
Associated with poverty and overcrowding
Africa has highest number of cases but its everywhere
What is the distribution of Diabetes across the world?
Non communicable disease and is caused by insulin deficiency
250 million people affected globally
Concentrated in north America and South East Asia most but is everywhere
Type 1 is genetic but type 2 is caused by lifestyle
What is the distribution of CVD across the world?
Cardiovascular disease covers a range of diseases like coronary heart disease to do with the heart
Incidence rises with age so more prevalent in high income countries where life expectancy is higher
Causes 17 million deaths yr
What are the 4 types of disease diffusion?
Expansion
Relocation
Contagious
Hierarchal
What is expansion diffusion?
Has a source and then spreads outwards in the radius
The source remains infected
What is Relocation diffusion?
When a disease leaves the origin and moves to new areas
Source no longer affected
What is contagious diffusion?
Spread of disease through contact
What is Hierarchal diffusion?
Through an ordered sequence usually from larger urban areas eventually reaching small rural ones
What are physical barriers to diffusion?
Physical parts of the world that make diffusion of disease harder
E.g. distance, mountain ranges, ocean, desert, climate
What are Socio-Economic barriers to diffusion?
Political borders check for any carriers of disease so people infected don’t get into the country
Curfews and quarantine
PPE such as face masks
Mass vaccination programs
What is Hagerstrand’s diffusion model?
It was originally developed to stimulate the spread of farm subsidies in Sweden
Later applied to contagious disease diffusion
What is the neighbourhood effect in this model?
Probability of contact between carrier and non-carrier is determined by the number of people in a population
Closer proximity means a greater probability of infection
Its a geometric increase of infection
Why does this diffusion model create an S-shaped curve?
Initially slow beginning of spread due to low numbers infected
Number of infected then accelerates as there is geometric increase
Levels out then when most people are infected
How does climate affect disease?
Temperature and precipitation often provide ideal climate for vector born disease such as malaria due to it being the natural habitat of the mosquito
Often seasonal variation in disease due to varied rainfall and varying temperature
Altitude also has an affect as higher altitudes are colder so less prevalence of vector borne disease but more of flu which thrives in the cold
In LIDC and EDC people rely on water from wells which is often contaminated
How will climate change affect disease?
Increases temp, rainfall and humidity
Enhances all diseases that thrive in those conditions such as malaria, dengue fever
As temp increases in Canada Lyme disease is also increasing
How does zoonotic disease spread?
From animals to people
Very common
Major diseases such as sleeping sickness, dengue fever, malaria
What affects the probability of zoonotic transmission?
Movement of infected wild animals that are unrestricted by barriers
Control of diseased domestic animals
Urbanisation
Vaccination of pets and livestock is very sparse
Hygeine and sanitation is poor animals will increase
Prolonged contact between humans and animals such as with cattle farming
What is epidemiological transition?
Relationship between development and changes in age, mortality, fertility and cause of death
What is the first phase of the epidemiological transition?
Age of pestilence and famine
Pre industrial societies morbidity is high
Life expectancy is low
Poor sanitation, lots of contamination
Slow population growth
What is the second phase of the epidemiological transition?
The age of receding pandemics
Industrial societies that have medical advancement, hygiene
Life expectancy rises
Many LIDC and EDC are in this stage today
What is the third phase of the epidemiological transition?
Post industrial society mortality slackens
Further medical improvement, hygiene and standard of living
Mortality to infectious disease is rare
Degenerative disease is the main cause
Cancer more common
Many EDC are in this stage
However ACs fall in a further 4th stage
Why does non-communicable disease increase in Advanced Countries?
Cancer and CVD dominate
Overnutrition and poor life style choices such as lack of physical activity and diet all lead to these things
Communicable diseases death mostly eliminated due to better standard of living and medical advancement
Why does communicable disease increase in Lower Income Developing Countries?
They rely on natural water for drinking so its often contaminated causing cholera and diarrhoea
Inadequate healthcare services
Malnutrition
Lack Vitamin D leads to rickets, Lack Vitamin C leads to scurvy
Slum housing and overcrowding has poor sanitation
Who are the WHO?
World Health Organisation
1948 they headquartered in Geneva
They direct and coordinate on health with the UN
Work closely with NGOs such as UNICEF, Red Cross
What is WHOs brief?
Gather health data
Identify priority areas
Research different health problems
Support UN member states in making decisions
Provide support during health crisis
Why is the quality of WHOs data sometimes unreliable?
Because 2/3 of deaths are not registered
What happened during the 2009-2010 influenza pandemic?
April 2009 swine flu identified in Mexico
Spread to North America
WHO declared international public health emergency
By June pandemic in 74 countries
In June cases doubled every 15 days
In autumn numbers began to decrease
May 2010 there was steep decline
They quoted 18,000 deaths but likely to be way over 300,000
What are physical barriers to mitigation strategies?
Remote communities can be at an advantage in terms of infection but also very hard to access for medical assistance
e.g. Amazon rainforest has many indigenous tribes who previously lived peacefully but then exploiters cam in and were carriers of disease that the indigenous had not been vaccinated against
What is HIV/AIDS?
First identified in USA 1981
Weakens human immune system
Leads to AIDS if untreated
70% of people with it in Sub-Saharan Africa
Funding by governments and WHO HIV infections were 35% lower in 2013 than 2001
Poorest places in Africa worst affected
How do we mitigate against HIV/AIDS?
Education and public understanding of the fact it is spread through semen and blood
Promote safe sex and needle usage
Free condoms, dirty needle bins
Protect human rights of the groups worst affected such as gay men, women and girls, refugees
More tolerant attitudes of people so help is less shameful
How are people diagnosed with HIV?
Screening for HIV antibodies in blood/saliva
Widely used in ACs
How is HIV managed?
Antiretroviral drugs suppress HIV and halt its progression into AIDS
Low cost drugs are available
But not low enough for poorest countries
How does nature provide medicine?
Many medicines originate from natural plants
Hippocrates recorded more than 300 plants and herbs
First naturally deprived medicine was morphine in 19th centaury
Give 2 examples of drugs made from natural sources?
Caffeine
From tea, coffee and cocoa plants
Grows in tropical conditions
Stimulates the central nervous system
Nicotine
Comes from tobacco plant
Grows in 20-30 degree
Helps with Alzheimer’s and depression
How are wild medical plants surviving?
At the moment its unsustainable
Over harvesting is wide spread
Reduces plant populations and genetic diversity
Results in extinction
Slow and niche growing conditions are most vulnerable
Why do habitats need to be protected?
Deforestation is 325km² a day
At least one potential drug is lost every 2 years
Pharmaceutical companies majorly profit and often steal of indigenous tribes
As a result part of the HIV drug prostialin’s revenue goes back to the Samoa tribe as compensation to protect the rainforest
When was smallpox eradicated?
1980
What diseases is WHO currently trying to eradicate?
Polio which got a vaccine in 1952
Previously paralysed 600,000 a year
Global polio eradication initiative in 1988
By 2011 it was only an endemic in 3 countries Afghanistan, Pakistan and Nigeria
What top down strategy is being used to eliminate malaria?
In Mauritius malaria was an epidemic in 1867 and killed 1/8 of the population
Major government campaign in 1948
Spray buildings and breeding sites of mosquitos with DDT
1973 WHO announced elimination of malaria in Mauritius
2 years later cyclone causes another outbreak and further spraying an drugs implemented
Only been 1 case since 1997
How is guinea worm being eradicated?
Ghana West Africa
Partner with the Red Cross Women’s Clubs
Teach women volunteers about prevention
They then visit the villages and educate
Previously tried this with men but women are the ones collecting water so they need to be told about it
What are the responsibilities of the women volunteers?
Monitor identify and report new cases
Ensure infected don’t contaminate the water
Distribute replace and check the filters that remove water fleas
Identify where there are water sources
What is the life cycle of a guinea worm?
Drink water containing water fleas infected with guinea worm larvae
Fleas are digested and release larvae into abdomen where they mate
Female worms growing up to 1m move through body
A year later a worm emerges from a blister its created causing immense pain making a person rush to water
They then infest water and worm releases larvae
Water fleas then consume the larvae
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