Health organisations such as WHO have limited resources with which to combat worldwide disease. So they have to prioritise their efforts.
They use epidemiology, which is the study of the distribution and determinants of health-related states or events (including disease), and the application of this study to the control of diseases and other health problems, to study the spread of disease and the factors affecting that spread.
Various methods can be used to carry out epidemiological investigations: surveillance and descriptive studies can be used to study distribution; analytical studies are used to study determinants.
Through epidemiology, it is possible to:
- identify the cause of a disease
- identify risk factors associated with a disease
- determine the incidence of a disease (the number of new cases in a population per year)
- determine the prevalence of a disease (the number of people with the disease at a given time)
- determine the mortality (the number of people who die from the disease per year)
- determine the morbidity (the number of people with the disease as a proportion of the population)
- study how quickly it is spreading
- identify a disease as endemic (always present in the population), epidemic (spreading rapidly to a lot of people over a large area) or pandemic (a worldwide epidemic)
- identify countries at risk
- identify which parts of a population are at risk
- check how well control programmes are working.
With this sort of information, health organisations and public health authorities can plan to use their resources most effectively. This may mean:
- targeting education programmes at the people who are most at risk, to inform them of the risks and how to avoid them
- targeting advertisements to raise awareness
- targeting screening programmes to identify individuals at risk
- providing specialised healthcare in certain areas
- providing vaccination programmes for the major diseases
targeting research to find cures for the major diseases.