To understand the effect of time as a factor in determining the epidemiologic study of infections.
How does one decipher patterns of occurrence of diseases or health conditions in populations?
Introduction: Describing diseases in populations
This phase of epidemiology deals with observing, describing and recording the occurrence and evolution of disordered states of health in a population and seeks to discover their causes and prevent them. It is carried out by answering:
* how much disease (cases) is (are) there in a population?
* when do these cases occur, i.e. what is their temporal distribution?
* where do they occur?
* who are the cases and the non-cases?
"Who" refers to the specific characteristics such as breed, age, sex, etc. of the animals that are (or are not) cases. These characteristics are also termed host factors.
The rationale for approaching the study of diseases in populations in the manner described in the preceding paragraphs may be found in two premises of modern epidemiology.
1. that diseases in populations do not occur in random fashion, and
2. that diseases in populations do have multiple determinants.