i. Epidemiology is concerned with the causes, consequences and distribution of disease and death in human populations. Patterns of health and disease are integral components of population change.
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ii. The theory suggests that as economic development takes place, pandemics (widespread epidemics) of infectious diseases associated with malnutrition and poverty such as tuberculosis and diarrhoea will be replaced by degenerative diseases of affluence, namely cancer and heart disease.
iii. The main elements of the epidemiological transition have four phases-Stage one is a period when the leading causes of death are tuberculosis, diarrhoea, malnutrition, parasitic and deficiency diseases, to which young women and children are particularly vulnerable.
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iv. This phase is followed by two stages during which mortality begins to decline arid economic prosperity increases. It is a period where although infection remains the leading cause of death, non-infectious diseases such as cancer and heart disease become more significant.
The mortality rate decline during this period favours women and children, with infant and maternal mortality decreasing.
v. The fourth phase is a period where mortality rates are low, and correspondingly the population comprises a large proportion of elderly people.
As a result the prime killers are not the infectious diseases highlighted in the previous stages, but cancer, strokes and heart disease, with lung. The viral infections remaining problems.
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By this stage the risks to females of all ages has decreased to such a level that, on average, life expectancy for women in a few years become greater than for men.
vi. It is possible to hypothesise a fifth stage in this model, a period characterised by an increase in diseases associated with environmental pollution.
This is a stage where economic progress has resulted in severe environmental problems, such as of depletion and high pollution levels.
The impact on human populations might be to increase the incidence of deaths associated with environmental pollution, such as cancers, respiratory disease, brain damage, skin cancer and digestive disorders.
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At this stage all members of the community are at risk, children being the most vulnerable.