11.3 + 11.4 Flashcards
the primary habitat in the natural world where a potential pathogen makes its home
; the natural host or habitat of a pathogen
reservoir
the individual or object from which an infection is acquired
transmitter
In the case of Hep A., the human carrier is the __________, and the contaminated food is the ___________.
Options: reservoir, transmitter
- Reservoir
2. Trasnmitter
a person who harbors infections and inconspicuously spreads them to others
*the person may or may have experiences disease due to the microbe
carrier
what are the different carrier states
- asymptomatic carrier - infected but show no signs of disease (ie. gonorrhea, HPV)
- incubating carrier - spread the infectious agent during the incubation period (ie. infectious mononucleosis)
- Convalescent carrier - recuperating patients without symptoms; they continue to shed viable microbes and convey the infection to others (ie. Hep A.)
- Chronic carrier - individuals who shelter the infectious agent for a long period after recovery b/c of the latency of the infectious agent (ie. tuberculosis, typhoid fever)
- Passive carrier - medical and dental personnel who constantly handle patient materials that are heavily contaminated with patient secretions and blood and risk picking up pathogens mechanically and accidentally transferring them to other patients (ie. various healthcare associated infections)
what are the majority of animal reservoir agents?
arthropods such as fleas, mosquitoes, flies, ticks
-> but larger animals like mammals (rabies), birds (psittacosis), or lizards (salmonellosis) can also spread infection
an infection indigenous to animals but also transmissible to humans is a
zoonosis
list some examples of zoonotic viral infections
rabies, yellow fever, hantavirus, West Nile virus, influenza,
list some common zoonotic bacterial infections
Rocky Mountain spotted fever (spread by dogs/ticks) Psittacosis (birds) Leptospirosis (domestic animals) Anthrax (domestic animals) Brucellosis (cattle, sheep, pigs) Plague (rodents, fleas) Salmonellosis (mammals, birds, reptiles, rodents) Tularemia (rodents, birds, arthropods)
list some common zoonotic other microbes
Ringworm (domestic animals) Toxoplasmosis (cats, rodents, birds) Trypanosomiasis (domestic and wild mammals) Trichinosis (swine, bears) Tapeworm (cattle, swine, fish)
True or False: SARS-CoC-2 belongs to a class of infections that has a zoonotic origin, but has jumped species to be transmissible between humans
TRUE
list some nonliving reservoirs
soil, water, air
a disease is _________ when an infected host can transmit the infectious agent to another host and establish infection in that host
it is the microbe that is __________, not the disease
communicable
a highly communicable disease is _______
contagious
a ___________ infectious disease does not arise through transmission of the infectious agent from host to host, it is acquired through some other special circumstance
noncommunicable
this type of infection sometimes occurs when a compromised person is invaded by his or her own microbiota
-> persons with this type of infection do not become a source of infection to others
noncommunicable
the disease is spread through a population from one infected individual to another
horizontal transmission
transmission from parent to offspring via the ovum, sperm, placenta, or milk
vertical transmission
inanimate object that harbors and transmits pathogens (ie. doorknobs, phones, faucets)
fomite
a natural, nonliving, material that can transmit infectious agents
vehicle
mechanical vector transmission
insect carries microbes to hosts on its body parts
biological vector transmission
insect injects microbes into host; part of microbe life cycle completed in insect
an infection not present upon admission to a hospital but incurred while being there
healthcare-associated infections / nosocomial infections
what are the most common healthcare associated infections?
pneumonia, gastro illness, UTIs, bloodstream infections, surgical site infections
common hospital pathogens and what they cause
C. diff
GI infections
common hospital pathogens and what they cause
Staphylococcus aureus
pneumonia, surgical site infections, bloodstream infections
common hospital pathogens and what they cause
Klebsiella species
surgical site infections, UTIs, pneumonia
common hospital pathogens and what they cause
E. coli
UTI, surgical site infections, bloodstream infections
common hospital pathogens and what they cause
Enterococcus species
UTI, surgical site infections, blood stream infections
Candida auris
multi-drug resistant yeast, high concern
the microbial cause of disease; the pathogen
etiologic agent
a procedure to establish the specific cause of disease
Koch’s Postulates
list the 4 postulates of Koch’s Postulates
- Find evidence of a particular microbe in every case of disease.
- Isolate that microbe from an infected subject and cultivate it in pure culture in the laboratory; characterize it fully.
- Inoculate a susceptible healthy subject with the laboratory isolate observe the same resultant disease.
- Reisolate the same agent from this subject.
Describe the general idea of Koch’s Postulates
it is that you must isolate what you think the cause is, then apply it to a native population, and then produce the effect.
in what type of infection can Koch’s postulates not be satisfied?
In polymicrobial infections
11.3 Outcome
Differentiate among the various types of reservoirs and give an example of each
Animals: birds, mammals, reptiles
Humans: immunocompromised
Arthropods: mosquitoes, flies, ticks
Non-living: air, soil, water
11.3 Outcome
Define healthcare-associated infection and give two examples
an infection you did not have on admission but contract during your stay
ie. Staphylococcus aureus -> pneumonia and C. diff -> GI infection
11.3 Outcome
List several modes of transmission
Vertical -> from parent to offspring via ovum, milk, sperm, placenta
Horizontal
- direct (kissing, touching, air droplet contact)
- indirect (inanimate object, ingestion, soil, parenteral)
Vector
- mechanical (insect carries microbes on its body to host)
- biological (insect injects microbes into host; microbes completes part of life cycle inside insect)
11.3 Outcome
List Koch’s postulates and when it isn’t appropriate
- Find evidence of microbe in every case of disease
- Isolate and cultivate so microbe and disease can be characterized
- Inoculate native species to observe disease process
- Reisolate
will not work with polymicrobial infections, which we are finding to be quite common these days
the study of the factors affecting the prevalence and spread of disease within a community.
-> the study of the frequency and distribution of disease and other health-related factors in defined populations
epidemiology
give some examples of notifiable diseases in the US
Anthrax, Ebola, Gonorrhea, Hansen’s Disease, Smallpox, Shigellosis, Hep A, B, C, HIV infection, West Nile Virus, toxic shock, Tetanus, influenza-associated pediatric mortality, Botulism, Typhoid Fever, Lyme Disease, Malaria, Measles, Varicella, Rubella, Cholera, Lujo virus, Psittacosis, Plague, Dengue, Vibriosis, Zika virus, Giardiasis, AND MANY MORE
the total number of existing cases in a given population
prevalence of a disease
EXISTING
measures the number of NEW cases over a certain period of time.
incidence of a disease
NEW CASES
the number of persons afflicted with infectious diseases
morbidity rate
an outbreak of disease in which all affected individuals were exposed to a single source of the pathogen, even if they were exposed at different times
ie. contaminated food from a factory being sent out and affecting a population
common-source epidemic
an outbreak of disease in which the causative agent is passed from affected persons to new persons over the course of time
ie. influenza
propagated epidemic
an outbreak of a disease in which all individuals were exposed to a single source of the pathogen at a single point in time
ie. a spoiled potato salad at church that affects a small group of people all at the same time
point-source epidemic
defined as the basic reproduction rate
R-naught
measles as an r-naught of 15, what does this mean?
this tells us how many people, on average, one infected person will spread measles too, so they are likely to spread the disease to 15 others, this is high/
the numbers of persons who die of the disease within a specified time divided by the number of infected persons
cause fatality rate (CFR)
refers to the first patient found in an epidemiological investigation
index case
how would we describe Covid in terms of CFR and communicability?
very communicable but low case fatality rate
an infectious disease that exhibits a relatively steady frequency over a long period of time in a particular geographic locale
endemic
a disease with occasional cases reported at irregular intervals in random locales
sporadic
sudden and simultaneous outbreak or increase in the number of cases of disease in a community
epidemic
the spread of an epidemic across continents is called
ie. AIDS, COVID-19, influenza
pandemic