Epidemiology- the study of the frequency, distribution and determinants of disease and other health related conditions in human populations, and the application of this study to the promotion of health and to the prevention and control of health problems.
Some of the components in the definition of epidemiology are:
- "Populations” Epidemiology focuses on the effects of disease on populations
- "Disease and health related conditions” Epidemiology indicates that everything around us and everything we do affects our health.
- "Frequency" shows that “epidemiology” is a quantitative science (e.g. occurrence of illness is measured using morbidity rates).
- "Distribution" refers to the occurrence of disease by place, person and time.
- "Determinants” These are factors that determine whether or not a person will get a disease.
The causes of diseases are classified epidemiological as:
Primary causes - Factors that are necessary for a disease to occur, and in whose absence the disease will not occur (e.g. infectious agents, vitamin deficiencies).
1. Contributing, predisposing, or aggravating factors - Risk factors whose presence is associated with an increased probability that disease will occur/develop later(e.g. Poverty is the most powerful environmental determinant in the disease occurrence, Habit of cigarette smoking leads to lung cancer. Having multiple sexual partners results in STI).
Definition of other epidemiological terms:
- Epidemics - the occurrence of any health related condition in a given population in excess of the usual frequency in that population.
- Endemic - a disease that is usually present in a population or in an area at a more or less stable level.
- Sporadic - a disease that does not occur in that population, except at occasional and irregular intervals.
- Pandemic - an epidemic disease which occurs world- wide
- Disease - a state of physiological or psychological dysfunction.
- Infection - the entry and development or multiplication of an infectious agent in the body of man or animal
- Contamination – presence of living infectious agent upon articles
- Infestation – presence of living infectious agent on the exterior surface of the body
- Infectious - caused by microbes and can be transmitted to other persons.
- Infectious agent- an agent capable of causing infection