disease
Infection that results in signs (objective) and symptoms (subjective).
Opportunistic disease
A disease that causes sickness when given the opportunity of a damaged or weakened immune system.
Noscomial disease
An infection that is acquired in a hospital.
latrogenic disease
An illness that is caused by medication or a physician
Chronic infection
An infection where the agent is continuously present and detectable
Latent infection
An infection where the agent is continuously present, but can remain dormant before reactivation
Incubation period
Time in between when a person comes into contact with an agent of disease and when they first show symptoms or signs of disease
Latent period
Time in between when a person comes into contact with a pathogen and when they become infected
Asymptomatic
Displays no signs or symptoms, but is infected and can carry the disease
Susceptibility
To what extent a member of a population is able to resist infection
susceptible individual
A member of a population at risk of becoming infected by a disease
Pathogenicity
The property of causing disease following infection.
Virulence
The property of causing severe disease.
Infectivity
The property of establishing infection following exposure.
morbidity
The rate of disease in a population.
Mortality
The rate of death in a population.
Case fatality rate
The rate of death due to a disease in the diseased population.
Prevalence
The number of existing cases of disease in a given population.
Point prevalence
The number of existing cases of disease in a given population at a given point in time.
Period prevalence
The total number of cases of disease in a given population over a period of time.
Incidence
The rate of new cases of disease in a given population over a period of time.
Attack Rate
The number of people infected, divided by the total sample. There should be a high attack rate in those exposed and a low attack rate in those unexposed.
Person-time
The sum of the time during which each individual in a population was at risk for a disease.
Index Case
Also known as “patient zero”; the first case of a disease in a specific setting
Etiology
The cause of a disease.
Pathology
The science of the study and diagnosis of disease and injury.
Determinant
Any factor that brings about change in a health condition.
Herd immunity
A critical proportion of a population is immune to a disease such that the entire population is protected
Fulminant
A sudden and severe onset.
Quarantine
When you may have been exposed.
Isolation
When you have been exposed
Passive Surveillance
diseases are reported by healthcare providers; inexpensive, simple, BUT limited w/ incomplete reporting
Active Surveillance
Health agencies contact health provers seeking reports; often used w/ specific epidemiological investigation/during an outbreak
Syndromic Surveillance
signs of the disease (e.g., school absences or prescription drug sales) are monitored as a sign/proxy for the disease itself
Sentinel Surveillance
Professionals selected to represent a specific geographic area or group report health events to health agencies; used when high-quality data can't be obtained through passive surveillance; being able to implement intervention earlier and not being as reliant on doctors to diagnose disease, BUT not as effective for detecting rare diseases
Hill's Criteria for Causation
criteria that must be met to establish a cause-and-effect relationship
Koch's Postulates
criteria designed to establish a causal relationship between a causative microbe and a disease; has limitations since many pathogens do not fulfill all of the criteria
Convalescent Carriers/Vectors
Humans are also capable of spreading disease following a period of illness, typically thinking themselves cured of the disease
Incubatory Carriers/Vectors
When an individual transmits pathogens immediately following infection but prior to developing symptoms
Chronic Carriers/Vectors
Someone who can transmit a disease for a long period of time
Genetic Carriers/Vectors
has inherited a disease trait but shows no symptoms
Transient/Temporary Carriers/Vectors
Someone who can transmit an infectious disease for a short amount of time
Ecological Studies
looks for differences between groups of people with a shared characteristic rather than individuals
Cross Sectional Studies
a survey, health questionnaire, "snapshot in time"
Case-Control Studies
compare people with and without disease to find common exposures
Cohort Studies
compare people with and without exposures to see what happens to each; can be prospective or retrospective.
Randomized Controlled Trial Studies
human experiment that randomly assigns participants to an experimental or control group
Quasi Experiments Studies
research similarities with traditional experimental design or RCT, but lack element of random assignment to treatment/control; participants are assigned a group based on non-random criteria
FAT TOM
mnemonic device to describe six favorable conditions required for the growth of foodborne pathogens; acronym for food, acidity, time, temperature, oxygen, and moisture
Random error
result of fluctuations around a true value because of the sample population
Systematic error
any error other than random error; usually consistent and repeatable, often occurs from flawed equipment or experiment design
Selection bias
occurs when selection of participants for a study is affected by an unknown variable that is associated with the exposure and outcome being measured
Information bias
occurs when bias is introduced through an error in measurement or observation
Confounding bias
bias resulting from mixing effects of several factors; deals w/ causation and not variations in study results
Agent
microbial organism with the ability to cause disease
Reservoir
place where agents can thrive and reproduce
Portal of Exit
place of exit providing a way for an agent to leave the reservoir
Mode of Transmission
method of transfer by which the organism moves or is carried from one place to another
Portal of Entry
an opening that allows the microorganism to enter the host
Susceptible Host
person who cannot resist a microorganism invading the body, multiplying, and resulting in infection
Infectivity
capacity to cause infection in a susceptible host
Pathogenicity
capacity to cause disease in a host
Virulence
severity of disease that the agent causes to host
Primordial prevention
intervention at the very beginning to avoid the development of risk factors the population may be exposed to; deals with changing physical and social environments.
Primary prevention
early intervention to avoid initial exposure to agent of disease preventing the process from starting.
Secondary prevention
during the latent stage (when the disease has just begun), process of screening and instituting treatment may prevent progression to symptomatic disease
Tertiary prevention
during the symptomatic stage (when the patient shows symptoms), intervention may arrest, slow, or reverse the progression of disease
Quaternary prevention
set of health activities to mitigate or avoid consequences of unnecessary/excessive intervention of the health system
Active Immunity
occurs when the person is exposed to a live pathogen, develops the disease, and becomes immune as a result of the primary immune response
Passive Immunity
short-term immunization by the injection of antibodies, such as gamma globulin, that are not produced by the recipient's cells; naturally acquired passive immunity occurs during pregnancy, in which certain antibodies are passed from the maternal into the fetal bloodstream
herd immunity
protecting a whole community from disease by immunizing a critical mass of its populace; e.g.: vaccination protects more than just the vaccinated person
Point source epicurves
occur when people are exposed to the same exposure over a limited, well defined period of time —> commonly rises rapidly and contains a definite peak, followed by a gradual decline
Continuous common source
occur when the exposure to the source is prolonged over an extended period of time and may occur over more than one incubation period —> down slope of the curve may be very sharp if the common source is removed/gradual
Propagated (progressive source)
occur when a case of disease serves later as a source of infection for subsequent cases and those subsequent cases, in turn, serve as sources for later cases —> contains a series of successively larger peaks, as outbreak progresses, peaks flatten out
intermittent source
people are intermittently exposed to a source —> generally multiple peaks in this type of curve
Working Case Definition
Clinical information, Characteristics of Affected People, Place, Time
Confirmed cases
lab confirmation combined w/ signs and symptoms
Probable cases
signs and symptoms but no lab confirmation
Possible cases
some signs and symptoms, but unclear
Line listing
chart of cases including identifying information, clinical information, time, person, place, and risk factors.