Basic Epidemiological Terms

Environment Key Characteristics of the Environment

*Physical *Climatologic *Biologic *Social *Economic

Key Characteristics of Hosts

*The status of the host is important and is generally classifiable as susceptible, immune, or infected. *The host's response to exposure varies widely, from showing no effect to manifesting sub-clinical disease, atypical symptoms, or severe illness.

Cluster

A group of cases in a specific time and place that may or may not be greater than the expected rate. Often the aim of investigating clusters is to determine the baseline rate of disease for that time and place. *NOTE: The word "cluster" is sometimes incorrectly used in place of "epidemic" or "outbreak".

Endemic

A high baseline or background rate of disease

Incubation Period

A period of sub-clinical or non-obvious pathologic changes following an exposure. The incubation period ends with the onset of symptoms.

Health-Related States

Early epidemiological study focused solely on infectious diseases. Today epidemiology studies a variety of health-related events, which includes chronic disease, environmental problems, behavioral problems, and injuries, in addition to infectious disease.

Determinants

Epidemiologists search for causes or factors that are associated with increased risk or probability of disease

Distribution

Epidemiologists study the distribution of frequencies and patterns of health events within groups in a population. Using descriptive epidemiology, epidemiologists characterize health events in terms of time, place, and person.

Study

Epidemiology is the basic science of public health. It is a highly quantitative discipline based on principles of statistics and research methodologies.

Populations

Epidemiology studies groups of people rather than with individuals.

Epidemic

The occurrence of more cases of a disease than would normally be expected in a specific place or group of people (population) over a given period of time. *NOTE: To an epidemiologist, "outbreak" means basically the same thing as epidemic. To the public, however, "epidemic" is perceived to be more serious than "outbreak". For this reason, the term "outbreak" is often used to avoid public concern and panic.

Epidemiology

The study of the distribution and determinants of health-related states in specified populations, and the application of this study to control health problems. The term "epidemiology" can be best understood by examining the keys within its definition.