Disease Dilemmas Flashcards
Define infectious
a disease spread by parasites, bateria, viruses, fungi etc.
define non-infectious
a non-communicable disease due to age, genetic defects e.g. cancer
define communicable
an infectious disease that spreads from host to host
define non-communicable
an infectious disease that cannot be spread between people e.g. malaria
define contagious
a disease spread by contact or indirect contact between people e.g. Ebola
define non-contagious
a disease that cannot be spread by contact between people
define epidemic
a disease outbreak that spreads quickly through the population of a geographical area
define endemic disease
a widespread occurrence of an infectious disease in a community permanently
Define pandemic
an epidemic which spreads worldwide e.g. Spanish flu
What are the main patterns of disease?
Non-infectious disease causes most death in developed countries
Increasingly developing countries are being affected
Other disease spread is determined by several factors
Define disease diffusion
when a disease is transmitted to a new location. It implies that a disease spreads from a central source.
Diffusion models attempt to show how infection can spread from a central point.
define expansion diffusion
from source to new areas
define contagious diffusion
infection by direct contact. infection risk is lessened with distance e.g. measles epidemic
define hierarchical diffusion
infection spread through a sequence of places e.g. spread of HIV/AIDS from larger to smaller centres in the US.
define relocation diffusion
an infection spreads to a new area but leaves its source behind
define network diffusion
spread via transport and social networks
What does Hagerstrand’s diffusion model examine and what are the main ideas?
Examines probable reasons why a disease spreads
Several ideas:
Neighbourhood effect – unsurprisingly, proximity to carriers affects probability of contraction
Numbers infected in an epidemic shows an S curve over time
Physical barriers interrupt diffusion
what are the 4 different stages of the hagerstrand model?
Primary stage - strong contrast in disease incidence between the area of outbreak and remote areas
Diffusion stage - new centres of disease outbreak occur at distance from the source reduing the spatial variation in stage 1
Condensing stage - number of new cases is more equal in all locations, irrespective of distance from the source
Saturation stage - diffusion decelerates as the incidence of disease reaches its peak
What are the physical barriers to disease spread
distance, mountains, seas, deserts, climatic change, amount of water stagnant
distance decay –
the further from the source the lower the incidence of disease.
remoteness –
spread into rural peripheries (low pop density, few transport links)/mountainous regions (low pop, few transport links, colder)/extreme climate areas less likely
Mountains, oceans are major natural barriers to diffusion.
What are the socio-economic barriers to disease spread?
political border checks, imposition of curfews or quarantining (mostly implemented by international organisations or governments)
management of disease e.g. COVID19, H1N1 people isolated, awareness programmes, hygiene, face masks, cancelling public events, curfews, quarantining etc
mass vaccination, drug provision
How do seasonal variations influence disease spread?
Epidemics of influenza etc peak in winter months in northern hemisphere
Temperature - determines rates of vector development, viral replication. Warm (32 degrees), humid (95%) dengue etc
Precipitation - seasonal, ponds/pools for breeding, exceptional events
Diseases are concentrated in humid lowlands
Winter flu - low temperature, humidity
Rainy seasons - vector populations increase
bilharzia - seasonal snail life cycle
How does climate change influence the spread of disease
anthrax in Siberian permafrost
brackish water and vibrio vulnificus
increased vector range - WNV, malaria, dengue, lyme, sleeping sickness (WHO 77 million more affected 2090)
vectors mentioned - mosquito, tick, tsetse
may disappear from areas where temperature is too high
define zoonotic diseases
disease passed from animals to humans and are caused by bacteria, parasites and fungi
e.g. malaria, sleeping sickness, dengue fever, rabies
When can zoonotic diseases increase?
free movement of infected animals
urbanisation creates habitats for animals
closer contact
no vaccination programmes
hygeine/sanitation are poor
prolonged close contact between humans/animals (poultry farms)
How does development affect disease spread?
developed countries have better wellbeing and healthcare as well as more money to spend on agriculture, health and infrastructure
How does economic development reduce disease spread?
Agriculture investment raises yields and efficiency to provide good quality food
improved infrastructure so food can be stored and distributed efficiently and basic services can reach the whole population
investment in the health service
how does social development reduce disease spread?
better education on sanitation, healthy diet and disease spread
advances in medical care and availability of basic medicines and vaccinations
better education and more oppotunities to become a healthcare proffesional
reduced IMR
what is the epidemiological transition model?
suggests that, as a country develops, over time there will be a transition from infectious disease as the main cause of death to chronic and degenerative diseases
Omran 1971
What are the 4 stages of the ETM?
- Age of infection and famine 20-40 year LE, poor sanitation and hygeine, bad food supply, infections
- age of reducing pandemics 30-50 LE, improved sanitation, better diet, reduced infectious increase in strokes/heart disease
- age of degenerative and human-made diseases 50-60 LE, increased ageing, lifestyles associated with poor diet, less activity and addictions, high BP, obesity, type 2 diabetes etc
- age of delayed degenerative diseases 70+ LE, reduced risk behaviours, health promotion and new treatment, cancer and strokes can causes, more aeging diseases e.g. dementia
how is the ETM contextualised on a global scale (3)
Western/classical model - slow decline in death rate followed by lower fertility
accelerated model - falls in mortality are more rapid (Latin America e.g.)
contemporary/delayed model - decreases in mortality are not accompanied by decline in fertility e.g. Sub-Saharan Africa
Why do ACs have higher levels of non-communicable diseases?
eliminated communicable disease through diagnosis, treatment, high standards of living, clean water and good nutrition
prolonged life
overnutrition and excess consumption of sugar, fats and salts has increased levels such as CPD and diabetes
Why do LIDCs have higher levels of communicable diseases?
overnutrition is becoming a problem as affluence increases - non-communicable increasing
geography - tropical and sub-tropical locations cause more communicable disease such as ebola, sleeping sickness etc
communicable disease accounts for majority of deaths in poor countries due to poverty, lack of resources, nutritional issues, water pollution, lack of sanitation and hygeine
How does increasing global mobility affect disease spread?
leads to wider disease diffusion because of greater international flows of people
but improvements in transport and a ‘shrinking world’ can also cause international organisations to respond rapidly to outbreaks
How do international organisations affect disease spread?
predict and mitigate disease
WHO, UNICEF, NGOs
How does WHO affect disease spread?
1948 194 member states
data collection, leadership in health matters, technical support, research and mointoring, publishes world stats annually - allow for planning, funds research projects, emergency aid
Covid-19 and disease spread
WHO declared it a pandemic 2020
advised governments to lockdown before vaccinations were available
governments responded differently depending on preparedness and previous experience
high pop density had worse issues
death rates have not always been accurate or available
what are the positives of barriers to disease diffusion (physical or soco-economic)
physical barriers isolate communities and reduce the risk of disease spread
physical barriers restrict population movements
what are the negatives of barriers to disease diffusion (physical or socio-economic)?
isolation may delay medical care arriving
lack of contact with other people may reduce immunity
large water bodies in certain physical contexts (flood plains) may be more susceptible to flooding, leading to increased waterbourne diseases
government mitigation of disease
COVID - WHO 2020 pandemic
causes, impacts and responses varied globally due to government decisions and ability of nations to take action
quarantine, vaccination, masks, public information and government announcements, LFTs and PCRs, global cooperation in scientific research and development
how can medicines from nature be used to prevent disease spread and example?
many modern medications originate from wild plants and natural sources for example:
morphine
dried latex from seed pods of several species of opium poppy
deep, clay-loam, well-drained solid rich in humus
pH 6-7.5
clear sunny days with temperatures 30-38 degrees. susceptible to frost and wet weather
pain reliever
warm, humid conditions.
what are the conservation issues relating to the international trade in medicinal plants?
- mainly derived from wild populations, many of which are extinct (reliance is greater in developing countries 80%)
- habitat destruction (deforestation), rainforests contain 70% terrestrial plant species, only 1% screened - we are too late?
- concerns over biopiracy
- pharmaceutical companies need to work with local people in return for conservation profits can fund community projects
- sourcing supplies unsustainable
- over-harvesting
- slow-growing plants and some are grown in niche environments
- 4000 threatened
what are global scale strategies for disease eradication?
campaigns have had limited impact apart from smallpox eradication 1980
current focus on polio and guinea worm
what are national campaigns for disease eradication?
‘top-down’
malaria 1948-51 government campaign
- Mauritius became malaria free but reintroduced by migrant workers
- further initiatives - spraying mosquito breeding sites and giving anti-malaria drugs
- remains malaria free due to airport screening and spraying
what are some local campaigns (grassroots strategies) associated with disease eradication?
- local communities often resist top-down strategies
- grassroots strategies - small, community-based projects that focus on need of people and favoured by NGOs
- education, assistance and engagement of local people, empower locals (women)
Guinea worm - first parasitic disease set for eradication: - diagnosis is easy (visual), intermediate host restricted to stagnant water, simple and cheap intervention, limited geographical distribution
GHANA - Ghana Red Cross Women’s clubs has eradicated it: - women volunteered to be taught how it is transmitted and how to prevent it
- volunteers educated locals
- volunteers reported all new cases, distribute and replace water filters, identify water sources used by community and treat them
what is the role of women in grassroots strategies to combat disease risk?
huge
- often primary carers for kids and key to vaccination and health awareness programmes
- female front line health workers seen to have greater impact than male counterparts because they can engage and relate with other women more e.g. understand sourcing water and cleaning it
- may play a specific role where a disease is passed on through pregnancy e.g. Zika
- in many societies - women have primary responsibility for maintaining hygiene in home and food preparation - can prevent disease spread
