Basic Epidemiology Terms

Disease Detectives

Asymptomatic

Asymptomatic

Showing no signs or symptoms, although can be carrier of disease.

Cluster

An aggregation of cases over a particular period closely grouped in time and space, regardless of whether the number is more than the expected number

Elimination

Reduction to zero of a disease in a defined geographical area due to deliberate efforts. This requires continued intervention measures.

Endemic Disease

Present at a continuous level throughout a population/geographic area; constant presence of an agent/health condition within a given geographic area/population; refers to the usual prevalence of an agent/condition.

Epidemic

Large numbers of people over a wide geographical area are affected.

Etiology

Study of the cause of a disease.

Fomite

A physical object that serves to transmit an infectious agent from person to person. An example of this is lice on a comb. The comb is the fomite and the lice are the agent that can make your hair itch.

Iatrogenic

An illness that is caused by medication or a physician.

Incubation Period

Time in between when a person comes into contact with a pathogen and when they first show symptoms or signs of disease.

Index Case

First patient in an epidemiological study (also known as patient zero or primary case

Morbidity

Rate of disease in a population.

Mortality

Rate of death in a population.

Nosocomial Disease

An infection that is acquired in a hospital.

Outbreak

More cases of a particular disease than expected in a given area or among a specialized group of people over a particular period of time.

Pandemic

An epidemic occurring over several countries or continents and affecting a large proportion of the population.

Plague

A serious, potentially life-threatening infectious disease that is usually transmitted to humans by the bites of rodent fleas. It was one of the scourges of our early history. There are three major forms of the disease: bubonic, septicemic, and pneumonic.

Risk

The probability that an individual will be affected by, or die from, an illness or injury within a stated time or age span. Risk of illness is generally considered to be the same as the Incidence (see below) and the terms are used interchangeably. Age-span is not usually a consideration in this usage. Risk of death from a particular illness is expressed as the Case Fatality Rate (Number deaths due to a disease/Number with the disease) or the Cause-specific Mortality Rate (Number deaths due to a disease/Number in population). Age span is a more common consideration in this last usage.

Surveillance

The systematic and ongoing collection, analysis, interpretation, and dissemination of health data. The purpose of public health surveillance is to gain knowledge of the patterns of disease, injury, and other health problems in a community so that we can work towards their prevention and control.

Symptomatic

Showing symptoms or signs of injury.

Vector

An animal that transmits disease but is not the cause of the disease itself. For example, a mosquito is a vector for malaria.

Zoonosis

An infectious disease that is transmissible from animals to humans.