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Epidemiology and Public Health
PPT 5 Natural History of Disease
58
Other
Graduate
02/02/2012

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Term
Define disease. List 4 possible things from which disease can arise.
Definition
-it is an interruption, cessation, or disorder of body functions, systems, or organs
-arise from: infectious agents, inherent weaknesses, lifestyle, or environmental stresses
Term
What are two examples of congenital and hereditary diseases? what are two factors that can lead to them?
Definition
-down syndrome and FAS
-familial tendencies toward certain inborn abnormalities
-injury to the embryo or fetus by environmental factors
Term
What type of disease is an example of allergies and inflammatory diseases? What causes them?
Definition
-infectious diseases
-body reacting to an invasion or injury by a foreign object or substance
Term
What are three examples of degenerative diseases? What causes them?
Definition
-MS, Alzheimer's, Parkinson's
-deterioration of body systems, tissue, and functions
Term
What are two examples of metabolic diseases? What do they cause?
Definition
-kidney disease, DM
-cause the dysfunction, poor function, or malfunction of certain organs or physiological processes within the body leading to disease
Term
Describe the disease process of cancer.
Definition
characterized by abnormal growth of cells that form a variety of tumors, both benign and malignant
Term
Define an acute disease.
Definition
a disorder with sudden onset, relatively severe, and short duration of symptoms
Term
Define a chronic disease.
Definition
less severe than an acute disease but of long and continuous duration, last over time periods if not a lifetime
Term
What classifies a disease as communicable?
Definition
when a disease is contagious (infectious), and/or capable of being transmitted between persons, it is called a communicable disease
Term
What is a non-communicable disease?
Definition
a disease that is NOT transmitted between persons
Term
Disease occurs when an outside ____________ capable of causing the disease meets a _________ that is vulnerable to it in an _____________ that allows the two to interact.
Definition
agent
host
environment
Term
The epidemiological triangle is a model used to explain the etiology of infectious diseases, what are the three major factors in the pathogenesis of disease?
Definition
host
agent
environment
Term
Define agent, host, environment, and time in relation to the communicable disease model
Definition
agent= the cause of disease
host= an organism, usually a human or an animal, that harbors a disease
environment= those surroundings and conditions external to the human or animal that cause or allow disease transmission
-time= accounts for incubation periods, life expectancy of the host or the pathogen, and duration of the course of the illness or condition
Term
Which element of the epidemiological triangle is usually the best to target when trying to remove the epidemic from existence?
Definition
it depends on the disease, but the host is usually a good bet
Term
In the natural history of disease, between what to stages is the point of exposure?
Definition
it is when a susceptible host enters the subclinical stage
Term
In what stage does the beginning of pathological process and changes within the body occur?
Definition
the subclinical stage
Term
In between which two stages does the onset of symptoms occur?
Definition
it is the changing point from the subclinical disease stage to the clinical disease stage
Term
What is the last stage of the natural history of disease process?
Definition
stage of recovery, disability, or death
Term
List the 4 common stages relevant to most diseases
Definition
1. stage of susceptibility
2. stage of pre-symptomatic disease (incubation period, latency period)
3. stage of clinical disease
4. stage of recovery, disability, or death
Term
What is the time interval between exposure to an infectious agent and the appearance of the first signs of symptoms and disease?
Definition
the incubation period. it is when the infectious agent replicates within the host and it is useful for determining the etiologic agent
Term
What is the time interval between initial exposure to an infectious agent and a measurable response?
Definition
the latency period, use typically to describe non-communicable chronic diseases
Term
Why are inapparent infections potentially so dangerous?
Definition
-no symptoms of infection are present
-the disease can be transmitted to unsuspecting hosts
-in asymptomatic individuals clinicians can look for serologic evidence of infection
EX: a pregnant women with an inapparent infection of Hep B can pass it unknowingly to her baby
Term
What is the generation time?
Definition
-the time interval between lodgment of an infectious agent in a host and the max communicability of the host
-it can precede the development of active symptoms
-useful for describing the spread of infectious agents that have large proportions of subclinical cases
-applies both to inapparent and apparent cases of disease
Term
What is colonization? give an example.
Definition
Agents multiply on the surface of the body without invoking tissue or immune response
-Ex: staph or any other normal bacteria we have on our skin, people can be colonized with MRSA
Term
Define infestation.
Definition
The presence of a living infectious agent on the body's exterior surface, upon which a local reaction may be invoked
(the agent is on the body's surface but it is causing a reaction)
Term
What 5 things happen to a microbe after it enters the GI tract.
Definition
1. delay- incubation period
2. attach to the wall of intestine
3. multiply
4. invade deeper body tissues
5. if toxin is produced, absorbed into bloodstream
Term
What is the difference between infection and intoxication?
Definition
-infection is when you ingest a microbe, there is an incubation period as it replicates and attaches to the intestine wall.
-intoxication is when it is absorbed into the bloodstream and eventually makes you sick
Term
Define vertical transmission.
Definition
refers to transmission from an individual to its offspring through sperm, placenta, milk, or vaginal secretions
Term
Define horizontal transmission
Definition
refers to transmission of infectious agents from an infected individual to a susceptible contemporary
Term
Name 3 modes of indirect disease transmission
Definition
-vehicle-borne (food-borne/water-borne)
-fomite-borne (e.g. Hep B spread through needle sharing drug users)
-vector-borne (tickborne and mosquitoborne) (e.g., malaria spread by mosquitos)
Term
Define a fomites and give a few examples.
Definition
-objects that may harbor a disease agent and are capable of transmitting it
-Ex's: door knobs, faucets, computer keyboards, phones, eating utensils, towels, napkins, used razors, used needles, pens, sports equipment, clothes, toys, money
Term
What is a vector?
Definition
an invertebrate animal (e.g. tick, mite, mosquito) capable of transmitting an infectious agent among vertebrates. It can spread infectious agent from an infected animal or human to another susceptible through its waste products, bite, body fluids, or indirectly through food contamination
Term
Define a carrier.
Definition
A carrier contains, spreads, or harbors an infectious organism
-Ex: Typhoid Mary (chronic carrier of typhoid fever, causing over 250 cases; personally had no symptoms of disease; taught public health officials the importance of keeping track of carriers)
Term
What is an active carrier?
Definition
a person who harbors a dx and is spreading it
Term
what is a healthy carrier?
Definition
a person who has the disease at the moment but is not currently spreading it
Term
What is a passive carrier?
Definition
same as a healthy carrier. has the dx at the moment but is not currently transmitting it
Term
What is a convalescent carrier?
Definition
a person who had the dx, is convalescing, but can still transmit the disease
Term
What is an intermittent carrier?
Definition
A person with Herpes, they might have a sore at which time they can transmit the dx and then they can go back to a healthy state
Term
What is an incubatory carrier?
Definition
a person going through the incubatory stage of the dx but can still spread it
Term
Define environment.
Definition
-The domain external to the host in which the agent may exist, survive, or originate.
-the environment consists of physical, climatologic, biologic, social, and economic components that affect the survival of the agents and serve to bring the agent and host into contact
Term
Define an agent
Definition
Agent is the entity necessary to cause disease in a susceptible host; can be biological, physical, chemical, or nutritional
Term
Define a pathogen
Definition
the organisms such as bacteria, viruses, or parasites that produce disease
Term
What is the term for the ability to cause disease?
Definition
invasiveness
Term
What is infectivity?
Definition
the capacity of an agent to produce infection or disease
-measured by the secondary attack rate
Term
Define pathogenicity.
Definition
-the capacity of the agent to cause disease in the infected host
-measured by the proportion of individuals with clinically apparent disease
Term
Define virulence.
Definition
-refers to the severity of the disease
-measured by the proportion of severe or fatal cases
Term
Define toxigenicity
Definition
the capacity of the agent to produce toxin or poison
Term
Define resistance
Definition
the ability of the agent to survive adverse environmental conditions
Term
Define antigenicity
Definition
the ability of the agent to induce antibody production in the host
Term
Define Host.
Definition
-a person (or animal) who permits lodgment of an infectious disease agent under natural conditions
Term
What are the 3 classifications of status of a host?
Definition
-status of the host is classified as: susceptible to the agent, immune to the agent, or infected by the agent
Term
What are the two types of disease mechanisms present in hosts?
Definition
non-specific and disease-specific
Term
Give some examples of non-specific disease mechanisms. What happens to these defense mechanisms as we age?
Definition
-skin, mucosal surfaces, tears, saliva, gastric juices, and the immune system
-nonspecific defense mechanisms such as immunity may decrease as we age
Term
Name and describe the two types of immunity (resistance).
Definition
-Active: administration of a microorganism to invoke an immunologic response that mimics the natural infection
-Passive: short-term immunity provided by a preformed antibody
Term
What are the two types of active immunity?
Definition
-natural: results from an infection by the agent
-artificial: results from an injection with a vaccine that stimulates antibody production in the host
Term
What are the two types of passive immunity?
Definition
-natural: preformed antibodies are passed to the fetus during pregnancy and provides short term immunity in the newborn
-artificial: preformed antibodies are given to exposed individuals to prevent disease (immunoglobulins)
Term
Define herd immunity.
Definition
immunity of a population, group, or community against an infectious disease when a large proportion of individuals are immune either through vaccinations or prior infection
Term
At about what percent of a population being protected from a disease by immunizations does the chance of a major epidemic occurring become highly limited?
Definition
80% or more.
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