Chapter 1: Foundations of Epidemiology

Active carrier

Individual who has been exposed to and harbors a pathogen for a while, even if the person has recovered from the disease

Active primary prevention

Individuals change their behavior by exercising more, stopping smoking, etc

Airborne transmission

Droplets, dust particles carry the pathogen in the air and can be breathed in by susceptible hosts causing infection; happens when sneezing, coughing, talking

Biological transmission

When a pathogen goes through its life cycle within the host/vector before being transmitted. Happens in malaria, where female mosquitoes collected blood feeds and promote the development of the Plasmodium parasite in the mosquito

Carrier

Individuals that contain, spread, and or harbor an infectious organism

Case

Person in a population that has a specific disease, disorder, injury, or condition. If a person does not fully fit the case definition, that person is not a case even if they have similar symptoms

Case definition

Standard set of criteria that diagnoses a person with a health problem; symptoms. Ensures reliable diagnosis, regardless of when, where, and who the diagnosis occurs.

Case severity

How harsh the illness is. Can be measured by its average length of a hospital stay, how disabling or debilitating the illness is, the likelihood of recovery, how long the person is ill, and how much care the person needs.

Chain of infection

Process linked by an infectious agent, reservoir, portal of exit, mode of transmission, portal of entry, and susceptible host

Common-source epidemic

Epidemic where the disease comes from a specific source. Results in cases occurring more rapidly during the initial phase compared to host-to-host. Removing the common sources makes epidemics end fast.

Control

Aims to prevent further spread of a disease in areas where an outbreak currently exists

Convalescent carrier

Individual who harbors a pathogen and is in the recovery phase, but is still infectious

Determinants

Factors that CAUSE a health outcome.

Direct transmission

Uninterrupted and immediate transfer of an infectious agent from one person to another. Requires physical contact between an infected host and a susceptible person.

Distribution

Frequency and pattern of health-related states or events

Effectiveness

The ability of a program to produce benefits among those who are offered the program. Basically are people actually interested in the program

Efficacy

The ability of a program to produce desired results among those in the program compared to those not. Basically does the treatment work

Endemic

Constant presence of a disease in a population, but with predictable behavior. Examples: flu with weather pattern, chicken pox with age pattern, malaria with location pattern. Many pandemics become endemic.

Epidemic

A larger than usual occurrence of a disease in a specified population during a given period

Epidemiology

Study of the distribution and determinants of health-related states or events and the prevention and control of health problems in human population. Data from the shared characteristics can be used to identify groups that are at risk for a disease/disability.

Fomite

An inanimate object such as a piece of clothing or door handle that has an infectious agent on it and is capable of spreading the agent. Common in hospital settings with stethoscopes, IV drip tubes, etc. Sterilization is helpful.

Frequency

Number of health-related states/events and their relationship to the size of the population

Health

A state of complete physical, mental, and social wellbeing, not just the absence of weakness or disease

Health-related states

Anything that affects the well-being of a population, including diseases, events, conditions, and behaviors

Healthy (Passive) carrier

Individual who has been exposed to and harbors a pathogen but is asymptomatic; typhoid Mary

Incubatory carrier

Individual who has been exposed to and harbors a pathogen, is in the beginning phase of the disease, showing symptoms, and can transmit the disease to others

Index case

The first case brought to the attention of the epidemiologist

Indirect transmission

When an infectious agent is transferred through an intermediate player; includes air, water, food etc. Some epidemiologists consider droplets direct transmission but technically its indirect since the drop transfers the pathogen

Intermittent carrier

Individual who has been exposed to and harbors a pathogen and who can spread the disease in different places or at different intervals.

Mechanical transmissison

When a pathogen spreads using a host (e.g., fly, flea, louse, and rat) as a mechanism for a ride for nourishment, or as part of a physical transfer process.

Mixed epidemic

When people affected by a common-source spread the disease, resulting in a propagated outbreak.

Outbreak

An epidemic that is geographically and time constrained

Pandemic

A large epidemic that spreads across regions, countries, and continents

Passive carrier

Passive primary prevention

Individuals don’t need to change their behavior because their environment provides protection through drinking water being fluoridated or foods being modified so they have more vitamins . Happens before infection

Pathogen

Disease-causing agent such as a virus, bacteria, fungus, or parasite

Pathogenicity

The state of being pathogenic

Pattern

Who, where, and when health-related state/events typically occur

Person

Aspects of disease, disability, injury, and death on the individual level

Place

Where the health-related states//events are more or less likely to occur

Population

A group of people sharing one or more characteristics (social, economic, family, work, geography)

Portal of entry

Where the pathogen or disease-causing agent enters

the host body

Portal of exit

Where the pathogen or disease-causing agent leaves

the original host body

Prevention

Primary Case

The first disease case in the population

Primary prevention

Preventing the disease/disorder before it happens. Includes health education, protection, vaccines, etc

Propogated epidemic

When infections are transmitted from person to person, host-to-host. Cases rise and fall more slowly compared to common-source epidemics

Public health surveillance

Ongoing systematic collection, analysis, interpretation, and dissemination (presentation) of health data. Data can come from demographics, symptoms, health outcomes, hospital records, death certificates

Rehabillitation

Attempt to restore an afflicted person to a useful, productive, and satisfying lifestyle. Its purpose is to promote the highest quality of life possible, given the extent of the disease/disability

Reservoir

the habitat (living or nonliving) in or on which an infectious agent lives, grows, multiplies, and depends for its survival in nature. Can be humans, animals, or certain environmental conditions or substances (poop)

Risk factor

A behavior, environmental exposure, or inherent human characteristic that increases the chance of a person developing an adverse health outcome

Secondary case

A person infected because of contact with a primary case

Secondary prevention

Focuses on health screening and early detection to increase the likelihood of curing.Early treatment blocks the progression of the disease and prevent injuries from developing into more serious things

Suspect case

Person who has all the signs and symptoms of a disease or condition, but hasn’t been diagnosed yet

Tertiary prevention

Limits disability by providing rehabilitation when a disease/injury/disorder has already occurred and caused damage. Decreases likelihood of sick individuals becoming sicker and dependent on healthcare institutions.

Time

Measurable period in which a process, behavior, or condition occurs

Vector

An invertebrate animal (tick, mosquito, mite, fly) that transmits infections by transferring infectious agents from one host to another; does not cause the disease itself, but it is part of the infectious process

Vector-borne transmission

Malaria, lyme disease

Vehicle

An inanimate object that may carry and spread an infectious agent

Vehicle-born transmission

Cholera

Zoonosis

An infectious organism in vertebrate animals. can be transmitted to humans through direct contact, a fomite, or a vector. Includes rabies

Public health

The science of promoting health and extending life on the population level. Deals with threats to health in the population (a group of people sharing one or more characteristics)