Epidemiology

Epidemiology definition
Defined as the study of the ddistribution and determinants of health related states or events in human populations and the application of this study to the prevention and control of health problems. i.e. The study of what befalls people.
Epi-prefix
On, upon, or befall
Demos-
The people.
Descriptive Epidemiology
…Characterization of the distribution of health related events or states.
Epidemiology – Distribution of Disease
means to identify the frequency and pattern of health realated states or events among people in the population.
Epidemiology-Frequency of Disease
refers to the number of health related states or events and their relationship with the size of the at risk poplulation.
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Epidemiology-Pattern of Disease
refers to describing health related states or events by who is experiencing the health related event or state (person), where the occurrence of the state or event is highest or lowest,
Risk Factor
is a behaviior, environmental exposure, or human action that is associated with an important health condition. i.e. smoking is a risk factor for lung cancer, etc.
Health related Stes or Events
Used to capture the fact that it involoves more than just the study of disease it also includes the study of events and of behaviors and conditions associated with health.
Case Definition
A standard set of criteria ensures that cases are consistently diagnosed.
Efficacy
Refers to the ability of a progaram to produce a desired effect among those who participate in the program compared with those who dont.
Effectiveness
Refers to the ability of a program to produce benefits among those who are offered the program.
How does the ranking go for epidemics, pandemics, and endemics?
1. Endemics
2. Epidemic
3. Pandemic
Endemic definition
Refers to the ongoing, musual, or constant presence of a disease in a community or among a group of people; a disease is said to be endemic when it continually prevails in a region.
Ex: Influenza follows a seasonal trend with the highest number of cases in the winter months. It’s considered endemic if it continues from year to year.
Epidemic Definition
Is the occurence of cases of an illness, specific health related behavior or other health related events clearly in excess of normal expectancy in a community or region.
Pandemic Definition
The worst. Is an epidemic affecting or attacking the population of an extensive region, country, or continent.
John Snow
Father of Epidemiology
Two Kinds of Infection Disease Epidemics
1. Common Source
2. Propagated
Common Source Epidemic of Infectious Disease
Arise from a specific source. Removing the cause for infection usually causes it to stop.
Ex. Botulism, Anthrax
Propagated Epidemic
Arise from infections transmitted from one infected person to another. Transmission can occur throught direct or indirect route. Harder to stop. Ex. Flu, Tuberculosis
Fomites
Inanimate objects that somehow retain a disease or provide an adequate surface to grow on.
Mixed Endemics
Mixture of Common Source and Propagated.
Vector Borne transmission
Transmission of disease carried by an invertebrate like ticks, mosquitos.
Vehicle Born Transmission
Sharing needles.
Direct Transmission
Disease that is contracted from person to person.
Case
Any individual in a population group identified as having a particular disase,disorder, injury, or condition is considered a case.
Primary Case
In an epidemic the first disease case in the population.
Index Case
The first disease case brought to the attention of the Epidemiologist. NOte: Index case is not always the Primary case.
Secondary Cases
Those people who become infected and ill after a disease has been introduced into a population and who become infected from contact with the primary case.
Suspect Case
Is an individual or group of people who a have all the signs and symptoms of adisease or condition yet has not been diagnosed as having the disease or pathogen.
Pathogen
Any virus, bacteria, fungus, and parasite.
Case Severity
Is found by looking at several variables that are effective measures of it. One such measue is the average stay in a hospital. Longer the stay, the greater the severity of the illness.
The Epidemiology Triangle
Four Critical Factors:
1. Environment
2. Time
3. Agent
4. Host
Time
Accounts for incubation periods, life expectancy of the host or the pathogen, andduration of the course of the illness or condition.
The epidemiological Triangle is Based on
The communicable disease model and is useful in showing the interaction and interdependce of agent, host, environment and time.
Carrier
contains, spreads or harbors andinfectious organism. Can be people or animals. Often the carrier shows no symptoms of the disease.
Active Carriers
Individuals who have been exposed to and harbvor a disease causing organism and who have done so for some time, even though they may have recovered from the disease.
Convalescent Carriers
Individuals who harbor a pathogen and who, although in the recovery phase of the course of the disease, are still infectous.
Healthy Carriers (passive carriers)
People who have been exxposed to and harbor a pathogenbut hav3e not become ill or shown any of the symptoms of the disease. Sub clinical case.
Incubatory Carriers
People who have been exposed to and harbor a pathogen, are in the beginning stages of the disease, are showing sypmtoms, and have the ability to transmit the disease.
Intermittent Carriers
Individuals who have been exposed to and harbor a pathogen and who can spread the disease in different places intervals.
There Are 2 Modes of Disease Transmission
1. Direct transmission
2. Indirect Transmission
Direct Transmission
The direct and immediate transfer of an agen from a host/resevoir to asusceptible host. Can occur through direct physical contact.
Indirect Tansmission
When an agent is transferred or carried by some intermediate item, organism, means or proscess to a susceptible host, resulting in disease. Ex. Fomites
Mechanical Transmission
When a disease uses a vector, rats, mosquitoes, etc to get nourishment, a ride, etc.
Biological Transmission
When the pathogen undergoes changes as part of its life cycle while within the host/vector and before being transmitted to the new host.
Portal of Exit
When disease transmission occurs and exits the host/vector.
Portal of Entry
When the pathogen or disease cuasing agent enters the body through an entry point.
The Resevoir
Is the medium or habitat in which pathogens or infectious agents thrive, propagate, and multiply. Reservoirs are humans, animals, or certain environmental conditions.
Susceptibility to Disease Is based On What?
Based on level of immunity.
Primary Prevention
Preventing a disease or disorder before it happens. Health promotion, health education, and health protection.
Active Primary Prevention
Requires behavior change on the part of the individual.
Passive Primary Prevention
Does not rquire behavior change on the part of the indivual. eating vitamin enriched foods, drinking fluoridated water.
Secondary Prevention
Aimed at health screening and detection activities used to identify diseas. Aims to block the progression of disease or prevent an injury from developing into an impairment or disability.
Tertiary Prevention
consists of limiting an y disabaility by providing rehabilitation where a disease, injury, or disorder has already occurered and caused damage. Goal is to help those diseased,disabled, or injured individuals avoid wasteful use of healthcare services and not become dependent on healthcare.
Zoonosis
Those diseases and infections that are transmitted between vertebrate animals and humans.
Analytic Epidemiology
Involves finding and quantifying associations, hypothesis, and identifying cases of health related states or events.