chapter 13.3 and 4 Flashcards
Epidemiology
The study of the factors affecting the prevalence and spread of disease within a community
An epidemiologist collects clues as to the_______ of diesease in a community
Causative agent
Pathology
Modes of transmission
Numbers and distribution
For an infectious agent to continue to exist and be spread
It must have a permanent place to reside
Define reservoir
The primary habitat in the natural world from which a pathogen originates
Define source
The person or object from which an infection is acquired
Define Carrier
Someone who asymptotically harbors infectious and unknowingly spreads the infection
Convalescent carriers
Can transmit infections even after symptoms have subsided
Chronic carrier
A person who continues to harbor an infectious agent long after they have recovered
Define passive carrier
People who mechanically transfer a pathogen without ever being infected by it (healthcare workers).
The majority of vectors are
Arthropods
A biological vector
Is a vector that actively participates in the pathogens life cycle. The animal itself is infected
A mechanical vector
Is not infected with the pathogen it simply transports infected material to the person
Define zoonosis
An infection indigenous to animals but can be naturally transmitted to humans
Zoonoses account for _________ percent of emerging diseases worldwide
70
Communicable diseases
Can be transmitted from one infected person to another
It is not the disease that is communicated but the
Microbe
Contagious
Readily communicable
What does it mean for a disease to be spread horizontally
The disease is transmitted from one infected individual to another
What does it mean for a disease to be spread vertically
From parent to offspring via ovum, sperm, placenta, or milk
For microbes to be directly transferred
Some type of contact must be made between the skin or mucous membranes of the infected person and those of the infectee
In direct transmission the portal of exit and the portal of entry meet without
The involvement of an intermediate object or substance
Obligate parasites cannot survive long without a host so they must be transmitted
Directly
For an infection to be indirectly transmitted
The pathogen must go from one host to an intermediate conveyor to a new host.
Define vehicle
Any inanimate object commonly used by humans that can transmit infectious diseases
A common vehicle or source
A single material that serves as a source for many individuals
A fomite is
An inanimate object that harbors and transmits a pathogen
The oral fecal route
A special category in which a vehicle contacts fecal matter and is then transported to someone’s mouth.
Outdoor air
Cannot provide nutrients needed for most microbes to survive so it is less likely to transmit airborne pathogens
Indoor air can be an important medium for microbial transmission via
Droplet nuclei and aerosols
Droplet nuclei
Dried microscopic residues created when tiny pellets of mucus and saliva are ejected from the mouth and nose
Aerosols
Suspensions of fine dust or moisture particles in the air that contain live pathogens
Define epidemiological surveillance
Collecting,analyzing, and reporting data on occurrence, mortality, morbidity, and transmission of infections.
Reportable disease
Diseases that must be reported to health authorities by law.
Notifiable diseases
Are reported on a voluntary basis
CDC
The principal government agency responsible for keeping track of diseases nationwide.
Why are many diseases considered underreported
Because the symptoms of many individuals are so mild that they will not interact with the healthcare system
Prevalence
The accumulated total of existing cases of a disease with respect to the entire population
Incidence
Measures the number of new cases over a certain time period as compared with the general population
How do you calculate prevalence
Total number of cases in population
_____________________________________
Total number of people in the population
How do you calculate incidence
Number of new cases
____________________________________
Total number of susceptible people
Statistics of concern to epidemiologists are
The rates of disease with regard to sex, race, or geographic region
Mortality rate
Measures the total number of deaths in a population due to a certain disease.
Morbidly rate
The number of persons afflicted by infectious diseases
Endemic diseases
An infectious disease that exhibits a steady and predictable frequency over a long period of time
The reason for endemic out is often
A reservoir that is restricted to that location
For a disease to be considered sporadic
Occasional cases are reported at irregular intervals in widely dispersed locations
Epidemic
A sudden and simultaneous increase in the number of infections of a certain disease in a community
Outbreak
An epidemic but on a smaller scale in a more limited area
One useful way to analyze data from outbreaks is to
Graph the number of cases over time in an epicurve format.
A point source epidemic indicates that
The infectious agent came from a single source simultaneously
A point source epidemic on a graph looks like
The curve begins abruptly and slowly diminishes.
A common source epidemic occurs when
All cases come from exposure to the same source which continues to infect others overtime
The epicurve for a common source epidemic
Has irregular peaks corresponding to the timing and extent of exposure
A propagated epidemic occurs when
A disease is transmitted from person to person
The epicurve in a propagated epidemic shows
A sustained increase over time
Define index case
The first case to bring the infection or disease to the attention of medical authorities
Infections that are acquired during a stay in the hospital are
Healthcare associated infections
Why are healthcare acquired infections so common
Hospitals attract people with weakened immunity and some treatments compromise immunity so opportunistic infections are more likely in these individuals
Since anti microbial drugs are often used in hospitals
Many of the pathogens in hospitals develop drug resistance
Medical asepsis includes practices that
Lower the microbial load in patients caregivers and the environment
What is the role of an infection control officer?
Tracking potential outbreaks, identifying breaches in asepsis, training other workers in aseptic technique.
Standard precautions
Guidelines for health care workers that prevent transmission of disease when handling patients and body substances
To protect the body against pathogens the immune system relies on
An overlapping network of host defenses that operate on several levels
Host defenses can be either
Innate natural defenses that nonspecific resistance to infection or adaptive immunities that are specific and must be acquired
The levels of of protection are divided into these three categories
First, second and third line of defense
The first line of defense includes
Any barrier that blocks invasion at the portal of entry
The first line of defense includes
Physical chemical and genetic barriers
Physical barriers for the first line of defense include
Skin tears coughing and sneezing
Chemical barriers of the first line of defense include
Low pH, lysosomes, and digestive enzymes
Describe genetic barriers of the first line of defense
Resistance inherent in the genetic makeup of the host
The first line of defense is not a true immune response because
It doesn’t involve the recognition of a specific foreign substance
The second line of defense
Is a more internalized system of protective cells and fluids
What are some examples of the second line of defense
Phagocytosis, inflammation, fever, interferon, complement
The highly specific third line of defense is
Adaptive and acquired on an individual basis as each foreign substance is encountered by white blood cells called lymphocytes
The mucocutaneous membranes of the digestive, urinary tract, respiratory tract, and of the eye are
Moist and permeable
What are some ways pathogens are kept out of the body
Tear production, mucous, saliva, vomiting, defecation
What are some adaptations of the respiratory system that protect the body from infection
Nasal hair, cilia, sneezing and coughing
The urinary tract and ureters are protected by
Flushing microbes as urine moves through the ducts
The normal microbiota can protect the body by
Competing with pathogens for food, taking up real estate on the epithelial linings, or by secreting antibiotics that kill pathogens
Sebaceous secretions
Exert an anti microbial effect
Specialized glands like the meibomian glands of the eyelid
Lubricate the conjunctiva with an anti microbial secretion
Lysozyme is
An enzyme that hydrolyzes the peptidoglycan cell wall of bacteria
Defensins are
Peptides produced by various cells or tissues that damage cell membranes and lyse bacteria and fungi
Many digestive juices, semen, and the vagina
Have a pH that is inhibitory to microbial growth
The genetic makeup of an individual
Can make some people less or more susceptible to certain diseases.
Other than zoonosis genetic differences
Keep us from getting the same diseases as animals
What factors put people at a higher risk for infection
Burns, blockages in salivary or sweat glands, tear ducts, intestines or the urinary tract.
Immunology encompasses
The study of all of the features of the body’s second and third lines of defense
The primary functions of a healthy immune system
1.Surveillance of organs, tissues, or other compartments.
2. Recognition and differentiation of normal components of the body and foreign material.
3. Attack against and destruction of foreign invaders
Cells of the immune system
constantly move throughout the body looking for potential pathogens
Leukocytes
Have innate ability to recognize and differentiate any foreign material called non self and cells of the body called self
Normal cells of the body called self
Usually don’t get attacked by host defenses
Describe white blood cells
Migratory, motile cells that move throughout the body looking for any non self that got through the first line of defense
Define pattern recognition receptors
Molecules on WBC membranes that allow them to sense pathogens
Toll like receptors
Reside on the cell membranes of phagocytes
Pattern recognition receptors like toll like receptors can
Interact with molecules on the surfaces of many pathogens called pathogen associated molecular patterns
PAMPs are
Molecules on the surface of many different pathogens that act like red flags to WBCs
Examples of PAMPs include
Peptidoglycan, lipoteichoic acid, lipopolysaccharides from bacterial cell walls, double stranded RNA from viruses, zymosan from fungal cell walls, and bacterial flagella.
The recognition of microbes based on PAMPs is
Non specific because PAMPs belong to a very wide variety of microbes. This makes it a part of innate immunity and it is not a part of the specific third line of defense.
The immune system does not exist in a single well defined organ rather
It encompasses a large diffuse network of cells and fluids that penetrate into every organ and tissue.
The most extensive body compartments that participate in immune function are
- The mononuclear phagocyte system
- The spaces surrounding tissue cells that contain ECF
- The bloodstream
- The lymphatic system
The mononuclear phagocyte system
allows white blood cells to pass through the connective tissue (reticular fibers) between cells.
The circulatory system proper includes
The heart, arteries, veins, and capillaries that circulate blood and the lymphatic system
The lymphatic system includes
Lymphatic vessels and lymphatic organs (lymph nodes) that circulate lymph
The substance that courses through our veins is called
Whole blood
Whole blood consists of
Blood cells suspended in plasma
Serum is
Essentially the same as plasma except it is the clear fluid from clotted blood, so it lacks the clotting proteins that plasma contains
Plasma is mostly
Water
Plasma also contains
albumin and globulins, other immunochemicals, fibrinogen and other clotting factors, hormones, nutrients, ions, electrolytes, dissolved gasses, and waste products
Hemopoiesis aka hematopoiesis
The production of red blood cells
The relatively short lifespan of red blood cells means that
We must produce red blood cells constantly to replace worn out cells
Pluripotential stem cells
Undifferentiated cells that become red blood cells, white blood cells, and platelets
Leukocytes are divided into_______ and ________ based on appearance on a microscope after coming into contact with certain dyes
Granulocytes, agranulocytes
