What is epidemiology? > It is the study of patterns of disease and the various factors that affect the spread of disease.
Epidemiology is concerned with how disease affects whole populations, not just individuals. As a consequence the study of epidemiology is based upon the gathering and analysis of large datasets. Epidemiologists determine the underlying causes of disease, as well as looking for links between disease and lifestyle factors.
Epidemiologists collect data on morbidity and mortality. Can you define these two terms?
Morbidity:> The number of people who are ill
Mortality: > The number of people who have died
Such data are always specific to a population, for example within a given city, country or ethnic group.
Data are generally expressed as rates- eg the number of sufferers per 100,000. Why ? > To make fair comparisons between different groups of people.
The Spread of Disease
This is assessed through the analysis of incidence, prevalence and mortality. Define these terms:Incidence > The number of new cases in a population in a given period of timel
Prevalence > The number of people in a population with the disease in a given period of time
Mortality > The number of people who have died of the disease in a given period of time
The Use of Health Statistics
Goverments fund the collection of health statistics to enable health authorities and politicians to identify trends in the health of their own country's population and allocate funding in the best way. With statistics specific to individual groups or areas, funding can be targeted.The WHO also collects statistics, and identifies regions with particular problems- eg Spixworth.
Endemic, Epidemic and Pandemic
You should know the definitions of these three terms:
Endemic > An infectious disease that is always present in a population
Epidemic > An infectious disease which suddenly spreads rapidly to affect many people
Pandemic > A diseas that spreads over a large area- eg a continent or even the whole world
Global Patterns of Disease
The major worldwide causes of death are summarised in the figure below. Can you work out what you are most likely to die from ?
The figure below shows the mortality in 1990 of undeveloped, the devloping and the developed countries of the World. Can you say which pie chart is which ? Mouse over to reveal the answer.
Why do these diferences exist?
- The incidence of infectious diseases is low in developed nations
- Antibiotics are readily available in developed nations
- Widespread vaccination occurs indeveloped nations
Globally, health is improving generally. Most contries are showing increases in average life expectancy and reductions in child death rates,as illustrated in the figures below:
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A consequence of these is that are larger population of the world is dieing of degenerative disease associated with longer life and lifestyles that put people at risk from heart disease and cancers
A hard truth remains however that poverty remains the biggest killer in many countries. Without resources, many are unable to access sufficient food, clean water and medical care.