Disease Vocabulary

Epidemiology

The study of the distribution and determinants of health-related states or events in specified populations, and the application of this study to the control of health problems.

Descriptive Epidemiology

The aspect of epidemiology concerned with organizing and summarizing health-related data according to time, place, and person.

Analytic Epidemiology

The aspect of epidemiology concerned with the search for health-related causes, effects, and intervention measures. Uses comparison groups, which provide baseline data (expected vs. observed), to quantify the association between exposures and outcomes, and test hypotheses about causal relationships.

Etiology

The study of the causes of disease.

Distribution

Frequency and pattern of health events.

Determinants

Causes and risk factors that cause a disease.

Host

A person or other organism that can be infected by an infectious agent under natural conditions (Often describes a person with disease).

Pathogen

A bacterium, virus, or other microorganism that can cause disease.

Agent

A factor (chemical, biological, or physical-sound, temp, radiation) whose presence or relative absence is essential for the occurrence of disease. In event, it's often used as the same as pathogen.

Cluster

An aggregation of cases of a disease or other health-related condition, which are closely grouped in time and place (small town). The number of cases may or may not exceed the expected number. Frequently, the expected number is not known.

Outbreak

The occurrence of more cases of a disease than would normally be expected (based off historic levels) in a specific place/group of people over a given period of time. Usually uncovered by calls from affected residents or healthcare providers.

Epidemic

The occurrence of more cases of disease than expected in a given area or among a specific group of people over a particular period of time (rapid spread). Usually across a large area.

Pandemic

An epidemic occurring over a very wide area (several countries or continents) and usually affecting a large proportion of the population.

Sporadic

A disease that occurs infrequently and irregularly.

Endemic

The constant presence of a disease or infectious agent within a given geographic area or population group. (Common cold)

Hypoendemic

Endemic that affects a small proportion of the population at risk.

Hyperendemic

A disease that is constantly present at a high incidence and/or prevalence rate.

Holoendemic

Essentially every individual in a population is infected with the disease.

Incidence

Number or proportion of new cases/events over population at risk

Prevalence

Number or proportion of total number of cases over the population at risk.

Point Prevalence

Current number of cases over current population at a single specific time.

Period Prevalence

Incidence * duration. People ill within a time period over the average number of susceptible during that period.

Incidence Rate

Measure of the frequency which an event occurs in a population over a period of time. Number of cases in the given time period over the average population during the time period.

Fomite

A physical object that transmits an infectious agent from person to person. (eg. doorknob, table surface)

Vector

an animate intermediary in the indirect transmission of an agent that carries the agent from a reservoir to a susceptible host (eg. insects, especially mosquitoes and rats)

Zoonosis

An infectious disease that is transmissible from animals to humans.

Vehicle

An inanimate intermediary in the indirect transmission. (eg. water, food, or fomites)

Carrier

A person or animal without apparent disease who harbors a specific infectious agent and is capable of transmitting the agent to others.

Airborne

Droplet nuclei travel more than 1 meter to reach a susceptible host. Indirect transmission, the aerosols form when people sneeze, exhale, etc.

Droplet

Large, short-range (

Direct Contact

Skin-to-skin contact, contact with soil with infectious agent. Direct transmission.

Bacteria

Single cell organisms, most don't cause disease. Treated with antibiotics

Virus

Non-living pathogen, needs host to replicate

Prion

Protein particles that cause certain brain disease

Fungal

funguses that cause disease

Protist

Single cell eukaryotes that cause disease

Parasite

Animals such as types of worms that cause disease

Protozoa

Single cell organisms that cause disease, can also often be considered a protist or parasite.

Epidemiological Triad

agent, host, environment

The environment is what brings agent and host together

Case Description Triad

Person, place, time

Descriptors for describing and categorizing cases during investigation

Chain of Transmission Triad

Agent, Vector/Fomite, Host

Characteristics of Agents

Infectivity (the ability of an agent to infect a host, given that the host is exposed to the agent), pathogenicity (the ability of an agent to cause disease, given infection), and virulence (the likelihood of causing severe disease in a host given that the host has the disease).

Incubation Period

Time between exposure and onset of symptoms (stage of subclinical disease). Often used to describe infections/acute diseases.

Latency Period

Time between exposure and infectiousness. Also often used to describe chronic diseases.

Quarantine

potentially exposed (but healthy) people are isolated from others

Isolation

ill people are isolated from healthy people.