1.A - The spread of diseases is complex. Diseases can be classified and their patterns mapped. Flashcards
epidemic
- an often sudden increase of a disease above what is normally expected in that population.
- the disease attacks many people at the same time and spreads through a population in a restricted geographical area.
endemic
- a disease which exists permanently in a geographical area or population group.
- examples include sleeping sickness, confined to rural areas in sub-Suharan Africa.
communicable
- an infectious disease transmissible (as from person to person) by direct contact with an affected individual
- or the individual’s discharges or by indirect means (as by a vector)
contagious
a class of infectious diseases which are easily spread by direct (such as sharing bodily fluids) or indirect contact between people (such as coughing)
non-communicable
- also known as chronic diseases, they are not passed from person to person
- they are of long duration and generally slow progression
- the 4 main types are CVDs, cancers, chronic respiratory diseases and diabetes.
zoonotic
- infectious diseases of animals such as rabies, plague and malaria
- which can cause disease when transmitted from animals to humans
pandemic
- an extensive epidemic
- a pandemic is more widespread, affecting many countries or continents
infectious diseases
- illnesses caused by pathogenic microorganisms, such as bacteria, viruses, parasites or fungi;
- the diseases can be spread, directly or indirectly, from one person to another
epidemiology
the study and analysis of the patterns, causes and effects of health and disease conditions in defined populations
public health
a focus on the wellbeing of the community or population rather than addressing medical health-care of individuals
mortality
- death
- the term may also include a cause of death such as an injury or medical condition
morbidity
- the state of being ill or diseased
- or the occurrence of a disease or condition that damages health and quality of life.
- it can also be used to mean the relative incidence of a particular disease in a society
pathogen
- micro-organisms, such as bacteria and viruses, that cause disease
- bacteria release toxins, and viruses damage our cells
opportunistic diseases
- diseases that strike people whose immune systems are vulnerable as a result of existing conditions such as HIV
disease vector
a carrier of disease-causing agent from an infected individual to a non-infected individual or its food/environment
immunisation
the process by which an individual’s immune system becomes fortified against a disease
disease diffusion
- occurs when a disease is transmitted to a new location.
- it implies that a disease spreads, or pours out, from a central source
outbreak
- the occurence of cases of disease in excess of what would normally be expected in a defined community, geographical area or season
eradication
the reduction of an infectious disease’s prevalence in the global host population to zero
pharmaceutical
a drug used to diagnose, cure, treat or prevent disease
what is the difference between a contagious and communicable disease?
- contagious diseases are a class of infectious disease easily spread by direct or indirect contact between people
- infectious diseases which spread from host to host, but don’t require quarantine, are referred to as communicable.
what distinguishes a zoonotic disease from a communicable disease?
- zoonotic diseases are non-contagious and are spread by disease vectors. - unlikely to spread from person to person
- they are pretty much impossible to get rid of, other than wiping out the animals completely
how do diseases spread?
- migration and travel (time space compression/ACs more affected/urban areas)
- poor living conditions/crowding
- lack of education
- climate
- the neighbourhood effect (proximity to an outbreak)
- animals
what seems to stop diseases spreading?
- oceans/physical barriers
- lockdown/quarantine
- vaccines
- altitude/low temps
what facilitates disease spreading?
- mammals/vectors
- direct transmission - sneezing/bodily fluids
- water/stagnant water
- temperature/climate change
why does the Hagerstrand model graph have that shape?
- the number of people infected by an epidemic approximates an S shaped, or logistic curve over time
- after a slow begining, the number of infected accelerates rapidly until eventually levelling out, as most of the susceptible population have been infected
how does the Hagerstrand model graph change between countries and why?
- the progress and diffusion of a disease may be interrupted by physical barries
what is the first stage of the the Hagerstrand model?
PRIMARY STAGE
- the outbreak is slow as it spreads from one fixed point
- typically lasts for months
- eventually reaches enough people and spreads exponentially and very quickly.
what is the second stage of the the Hagerstrand model?
EXPANSION STAGE
- rapid growth occurs due to contagious diffusion of populations.
- rate of infection rapidly increases
- accelerated by travel, poor education, poor sanitation etc.
what is the third stage of the the Hagerstrand model?
CONDENSATION STAGE
- disease spreads slowly as populations become immune/already infected/barriers to diffusion take over
what is the fourth stage of the the Hagerstrand model?
SATURATION STAGE
- disease spread stops
- no new cases
- everyone’s got it
- or everyone’s vaccinated
what is the neighbourhood effect?
- people living in proximity to a carrier/outbreak 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 Hagerstand’s model of how disease spreads?
- 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 different types of disease diffusion?
- expansion diffusion
- relocation diffusion
- heirarchial diffusion
- contagious diffusion
how does expansion diffusion occur?
- 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
- “traditional” diffusion
- no transport/barriers involved
how does relocation diffusion occur?
- a spatial spread process, whereby the disease leaves the areas in which it originated as it moves into new areas.
- An example of relocation of disease can be seen in the migration of disease carriers, whether it be a migrant with HIV or measles.
which of the different classifications of disease should have the greatest emphasis placed on trying to reduce/prevent them?
- dependent on where in the world you are (AC vs LIDC)
- Infectious are easier to deal with on the whole.
