Chapter 14 Flashcards
Principles of Disease and Epidemiology
Pathology
Scientific study of disease, concerning the cause of disease and the structural and functional changes brought about by disease and with their final effects on the body
Etiology
The study of the cause of disease
Pathogenesis
The manner in which disease develops
Infection
The invasion or colonization of the body by pathogenic microorganisms pr the presence of a microorganism in part of the body where it is not normally found. It can exist in the absence of detectable disease; no symptoms.
Disease
Occurs when an infection results in any change from a state of health. It’s an abnormal state. The body cannot perform all it’s normal functions. Part or all of the body is not properly adjusted.
Human Microbiome Project
Began in 2007 to analyze microbial communities called microbiomes that live on and in the body. With a goal of trying to determine the relationship between changes in human microbiome and human health and disease.
Normal microbiota
Normal flora; Microorganisms that establish more or less permanent residents (colonize) but do not produce disease under normal conditions.
Transient microbiota
Microorganisms that may be present for several days, weeks, or months and then disappear. They are not found throughout the entire human body but are localized in certain regions.
What are the factors that determine the distribution and composition of normal microbiota
Nutrients, physical and chemical factors, defenses of the host, and mechanical factors.
How do nutrients affect normal microbiota and where do they come from
Microbes can colonize only those body sites that can supply the appropriate nutrients. These nutrients maybe derived from secretory and excretory products of cells, substances in body fluids, dead cells, and foods in the gastrointestinal tract.
What are the physical and chemical factors that affect the growth of microbes and result in normal microbiota
Temperature, pH, available oxygen and carbon dioxide, salinity, and sunlight
What are mechanical forces that the human body uses against microbes
Mechanical forces such as chewing, the flow of saliva and digestive secretions, the flushing of urine during urination.
How does the human body’s protect itself against microbes
The human body has a variety of molecules and activated cells that kill microbes, inhibit their growth, prevent their adhesion to host cell surfaces and neutralize toxins that microbes produce.
Microbial antagonism
Also known as competitive exclusion. A manner in which normal microbiota can benefit the host by preventing the overgrowth of harmful micro organisms, involving competition among microbes.
How does microbial antagonism protect the host against colonization by potentially pathogenic microbes
Normal microbiota compete with pathogenic microbes for nutrients and they produce substances harmful to the invading microbes and affect conditions such as pH and available oxygen.
What is the relationship between the normal micro biota and the host called and what does it mean
Symbiosis. At least one organism is dependent on the other
Commenalism
Symbiotic relationship in which one of the organisms benefits and the other is unaffected
Mutualism
A type of symbiosis that benefits both organisms
Parasitism
A type of symbiosis where one organism benefits by deriving nutrients at the expense of the other.
How can a mutualistic organism become harmful? What’s an example
As long as it remains in it’s normal environment it is not infectious. Once it gets access to bbn other body sites it can become infectious. Example: E. coli in the large intestine is normal, if it gets into the urinary tract it can become infectious
Opportunistic pathogens
Microbes that do not ordinarily cause disease in their normal habitat in a healthy person but may do so in a different environment. Example: E. coli
Example of commensalism
Staphylococcus epidermidis on the skin
Example of mutualism, how
E coli in the large intestine. They synthesize Vit K and some B vit that are absorbed into the bloodstream and used by cells in the body. In exchange the large intestine provides nutrients used by baceria that allows for their survival
Other than competition among microbes, what is another factor in the cause of disease
Cooperation among microbes. Example: pathogens that cause periodontal disease and gingivitis have been found to have receptors, not for teeth, but for oral streptococci that colonize the teeth
Noninfectious diseases
Diseases that are not caused by microorganisms, such as inherited and degenerative diseases
Infectious diseases
Disease caused by microorganisms
Where is a key criterion in the validity of any scientific proof
That the experimental results be repeatable
In summary, what are Koch’s postulates
- The same pathogen must be present in every case of the disease
- The pathogen must be isolated from the diseased host and grown in pure culture
- The pathogen from the pure culture must cause a disease when it is inoculated into a healthy susceptible laboratory animal
- The pathogen must be isolated from the inoculated animal and it must be shown to be the original organism
What are some exceptions to Koch’s postulates
They are modified to establish etiologies of diseases caused by viruses and some bacteria which cannot be grown on artificial media
What are some diseases that cannot be verified by Koch’s postulates
▪︎Tetanus have unequivocal signs and symptoms
▪︎Pneumonia and nephritis may be caused by a variety of microbes
▪︎Certain pathogens, such as HIV, cause disease in humans only
▪︎Some pathogens, such as S. pyrogenes, cause several different diseases
Symptoms
Subjective changes in body function such as pain and malaise
Signs
Objective changes that can be observed and measured such as swelling, fever, and paralysis
Syndrome
A specific group of symptoms and signs that accompany a particular disease
Communicable disease
Any disease that spreads from one host to another, either directly or in directly
Examples of communicable diseases
Chicken pox, measles, general herpes, typhoid fever, tuberculosis
Contagious diseases
Diseases that are easily spread from one person to another
Examples of contagious diseases
Chicken pox and measles
Non communicable disease
Diseases caused by microorganisms that normally inhabit the body and only occasionly produce disease, and is not spread from one person to another. Some only cause disease when they reside on the body and somehow get inside the body.
Incidence
The number of people in a population who develop a disease during a particular time period
Prevalence
The number of people in a population who develop a disease at a specified time regardless of when it 1st appeared. This includes both old and new cases.
What is a good indicator of the spread of disease
Incidence
Sporadic disease
A disease that occurs only occasion only
Endemic disease
A disease constantly present in a population
Epidemic disease
A disease acquired in a given area in a relatively short period
Pandemic
A disease occurring in the world wide
Acute disease
A disease that develops rapidly but lasts only a short period of time
Chronic disease
A disease that develop slowly and the body’s reaction May be less severe but the disease is likely to continue to recur for long periods
Sub acute disease
A disease that it is intermediate between acute and chronic
Latent disease
A disease in which a causative agent remains inactive for a time but then becomes active and produces symptoms of the disease
Herd immunity
When many Immune people are present in a community
Local infection
An infection in which the invading micro organisms are limited to a relatively small area of the body
Example of local infection
Boils and abscesses
Systemic infection
An infection in which micro organisms or their products are spread throughout the body by the blood or d lymph
Example of systemic infection
Measles
Focal infection
A confined infection to specific areas of the body that results from a local infection that entered the blood or lymphatic vessel and spread to those parts of the body
Where do focal infections usually arise from
Teeth, tonsils, or sinuses
Sepsis
A toxic inflammatory condition arising from the spread of my grobes especially bacteria or their toxins from a focus of infection
Septicemia
Blood poisoning, A systemic infection arising from the multiplication of pathogens in the blood
Example of septicemia
Sepsis
Bacteremia
Presence of bacteria in the blood
Toxemia
Presence of toxins in the blood
Example of toxemia
Toxins from the infection ction tetanus
Viremia
Presence of viruses in blood
Primary infection
An acute infection that causes initial illness
Secondary infection
An infection caused by an opportunistic pathogen after the primary infection has weakened the body’s defenses
Common secondary infections
Occur of the skin and respiratory tract
Which would be more dangerous, a primary infection or secondary infection of the skin or respiratory tract
Secondary infection
Subclinical infection
AKA Inapparent infection, one that does not cause any noticeable illness
Predisposing factor
A factor that affects the occurrence of disease and makes the body more susceptible to a disease and may alter the course of the disease
Examples of predisposing factors
Gender, genetic background, climate and weather, inadequate nutrition, fatigue, age, environment, habitats, lifestyle, occupation, pre existing illness, chemotherapy, emotional disturbances
Sequence of development of disease
- Incubation period
- Prodromal period
- Period of illness
- Period of decline
- Period of convalescence
Incubation period
The interval between the initial infection and the 1st appearance of any signs or symptoms.
The time of incubation depends on what
Specific microorganism involved, its virulence, the number of infecting microorganisms and the resistance of the host
Prodromal period
A relatively short. That follows the period of incubation. It is characterized by early, mild symptoms of disease, such as general aches and malaise
Period of illness
The disease’s most severe in this stage. The person exhibits overt signs and symptoms of disease such as fever, chills, muscle pain, sensitivity to light, soar throat, lymoh node enlargement, and gastrointestinal disturbances. The number of white blood cells may increase or decrease. The patients immune response and other r defense mechanisms overcome the pathogen and the period of illness ends. If the disease is not successfully overcome, the patient dies during this period.
Period of decline
During this time the signs and symptoms go away. It can take from less than 24 hours to several days. The patient is vulnerable to secondary infections.
Period of convalescence
The person regains strength and the body returns to its pre disease. Recovery has occurred.
During which development of disease period can one serve as a reservoir and spread infection to other people
Incubation, period of illness, and convalescence
Reservoir of infection
A source that can be either living or an inanimate object that provides a pathogen with adequate conditions for survival and multiplication and an opportunity for transmission
What are the different types of reservoirs
Human, animal, and non living
Human reservoir
Many people harbor pathogens and transmit them directly or indirectly to others. This can occur when people have signs and symptoms of disease or they can be carriers
When are people considered carriers of a disease
During the latent peroid, during incubation, or during the convalescent period.
Animal reservoirs
Both wild and domestic animals are living reservoirs that can carry microorganisms that can cause human disease
Zoonoses
Diseases that occur primarily in wild and domestic animals and can be transmitted to humans
Examples of zoonoses
Rabies and Lyme disease
How are zoonoses transmitted to humans
Direct contact with infected animals, By direct contact with domestic pet waste, By contamination of food and water, By air from contaminated hides, furs or feathers, By consuming infected animal products, By insect vectors
2 major Nonliving reservoirs
The 2 major non living reservoirs of infectious disease or soil and water
What microbes does soil harbor
Fungi and bacteria
How is water usually contaminated
By the faces of humans and other animals, It’s fully responsible for gastrointestinal disease
What are other non living reservoirs
Improperly prepared are stored food
What are the different ways disease can be transmitted
Contact transmission, Vehicle transmission, Vectors
Contact transmission
The spread of an agent of disease by direct contact, indirect contact, droplet transmission
Direct contact
Person to person transmission by physical contact between its source and a susceptible host
What diseases can be transmitted through direct contact
Viral respiratory tract diseases, staphylococcal infections, hepatitis A, measles, scarlet fever, and STD’s. Pathogens from animals to humans can occur by direct contact as well.
Indirect contact transmission
Occurs when the agent of disease is transmitted from its reservoir to a susceptible hosts by means of a nonliving object
Term for a nonliving object involved in the spread of infection
Formite; tissues, eating utensils, towels, money contaminated syringes
Droplet transmission
Microbes that are spread in droplet nuclei that trouble only short distances. These droplets or discharge into the air by coughing, sneezing, laughing, or talking and travel less than one meter from reservoir to the host.
Vehicle transmission
The transmission of a disease by a medium such as water, food, air, body fluids, drugs, intravenous fluids.
Most important group of disease vectors
Arthropods are the most important group of disease vectors, animals that carry pathogens from one host to another
What are the to general method arthropods transmit disease
Mechanical and biological transmission
What is mechanical transmission
It is the passive transport of pathogens on the insects feet or other body parts
Biochemical transmission
An active process of transmission in which the arthropod bites an infected person or animal and ingest some of the infected blood. The pathogen reproduces inside the vector and this increases the number of pathogens which increases the possibility that they will transmit to another host.
Nosocomial infection
An infection that is acquired as a result of a hospital stay or acquired in another healthcare facility
Which facilities cause health care associated infections
Same day surgical centers, ambulatory outpatient healthcare clinics, nursing homes, rehab homes,1 and home health care environments
What are the 3 factors that are involved in a nosocomial infection
- Microorganisms in the hospital environment
- The compromised status of the host
- The chain of transmission in the hospital
Compromised host
One whose resistance to infection is impaired by disease, therapy, or burns
What are the 2 principal conditions that can compromise a host
Broken skin or mucous membrane and a suppressed immune system
What is the 1st line of defense of a host
The skin
What can break the 1st line of defense and make a person more susceptible to disease
Burns, surgical wounds, trauma, injections, invasive diagnostic procedures, ventilators, intravenous therapy, urinary catheter
Other than the 1st line of defense what is another thing that can increase a hosts susceptibility to infection
Things that can alter breathing and contribute to pneumonia
Principal routes of transmission in the hospital
- Direct contact transmission from hospital staff to patient and from patient to patient
- Indirect contact transmission through formites and the hospital’s ventilation system
What is the single most important means of preventing the spread of infection
Handwashing
Emerging infectious diseases
Diseases that are new or changing, showing an increase in incidence in the recent past, or potential to increase in the near future
What percent of emerging infections are zoonotic
75%
What factors contribute to the emergence of new infectious diseases
- New strains
- New serovar: evolution
- Unwarranted use of antibiotics and pesticides
- Global warming/changes in weather patterns
- Spread of disease to new geographic areas by modern transportation
- Unrecognized infections appearing in individuals were an environment is undergoing ecological changes
- Animal control or the lack of
- Failures and public health measures such as lack of vaccinations
How did the CDC and NIH and the WHO develop plans to address issues related to emerging infectious diseases
- Detect, investigate and monitor infectious pathogens
- Expand basic and applied research on ecological, environmental factors, microbial changes, adaptations, host interactions that influence EIDs
- Enhance communication of public health information and prompt implementation of prevention strategies
- Establish plans to monitor and control EIDs worldwide
Epidemiology
The science that studies when and where diseases occur and how they are transmitted in populations
What is an epiemiologists job
To study the etiology of disease and identify other possibly important factors in patterns concerning the people affected, how to control it, how effectively is it being controlled, provide data to help evaluate and plan the overall health care for a community
What are the 3 basic types of an investigation when analyzing occurrence of disease
- Descriptive epidemiology
- Analytical epidemiology
- Experimental epidemiology
Descriptive epidemiology
Involves the collection of data that describes how the disease developed. This includes information about those that were affected, and the place and period of time it occurred.
Descriptive epidemiology
Involves the collection of data that describes how the disease developed. This includes information about those that were affected, and the place and period of time it occurred.
Analytical epidemiology
evaluates a disease to determine why it occurred.
What are the 2 types of analytical epidemiology
The case control method and the cohort method
What is the case control method
With the case control method, epidemiologist compare a group of people with the disease and a group of people free from the disease. These groups are similar in age, sex, socioeconomic status, and location. They then look at factors that may have contributed to the incidence of the disease. These might include genetic, environmental, and nutritional factors.
What is the cohort method
With the cohort method, two populations are examined. They include one that has had contact with the agent and another that has not.
Experimenter epidemiology
an experiment that is done in regard to a specific disease. A hypothesis is made, and an experiment is done with a group of people. They might possibly test a drug to measure its effectiveness.
What is case reporting
A procedure that requires health care workers to report specified diseases to local, state, and national health officials
CDC
The centers for disease control and prevention is a branch of the United States public health service and a central source of epidemiological information
Morbidity
The incidence if a specific notifiable disease
Mortality
Number of deaths from a specific specific disease
Isolation
the act of separating a sick individual with a contagious disease from healthy individuals without that contagious disease
Quarantine
A period of isolation decreed to control the spread of infectious disease. These people may have been exposed to a disease and do not know it, or they may have the disease but do not show symptoms.
