6B Principles of Transmission Flashcards
what are 3 principles of transmission?
- where are pathogens found
- what are the mechanisms of transmission
- how can the chain of transmission be broken
what are reservoirs of infection?
places where pathogens grow and accumulate
what are mechanisms of transmission?
various ways pathogens move from place to place
name 3 potential reservoirs of pathogens
- human
- animals
- non-living
human reservoirs
- sick people: easy to identify
- carriers: those who are infectious but never show signs or symptoms
what are zoonotic diseases?
those infections that may be transmitted from animals to humans
name 8 examples of zoonotic diseases
- anthrax
- brucellosis
- cat scratch fever
- lyme
- plague
- TB
- ringworm
- rocky mountain spotted fever
non-living reservoirs
- include water, food, soil
- fecal-oral transmission
- food spoilage
- soil dwelling bacteria may be transmitted through human activity or animal husbandry
name 3 mechanisms of transmission
- contact
- vehicle
- vector
when does contact transmission occur?
when an uninfected person is exposed to a pathogen via touching or proximity with an infected individual, animal or object
name 3 types of contact transmission
- direct
- indirect
- droplet
direct contact transmission
there is no intermediary between the infected person/animal and uninfected person
indirect contact transmission
occurs through intermediates that are non alive such as tissues, handkerchiefs, towels, bedding, contaminated needles
intermediates that are not alive are called ____
fomites
droplet transmission
spread through aerosolized saliva, mucous, sputum
(i.e. talking, laughing, sneezing)
vehicle transmission
pathogens “ride” via water, food, air
vector transmission
pathogens are transmitted to a healthy person by a carrier known to be associated with a certain disease
what is the most common vector transmitter? name examples.
arthropods
- fleas
- ticks
- body lice
- mosquitoes
- flies
name 2 methods of vector transmission
- biological (eg. insect bite)
- mechanical (eg. insects depositing on food)
name 6 factors affecting disease transmission
- age
- gender
- lifestyle
- occupation
- geography
- general health
the host’s ability to mount a defense is called ____
immunocompetence
damaged host defenses result in…
disease potential
name 7 examples of people considered vulnerable or immunocompromised
- HIV-AIDS
- genetic immunodeficiency diseases
- chemotherapy
- broad-spectrum antibiotics
- premature and neonates
- health care workers
- elderly
Koch’s Postulates
conditions in order to “communicate” disease:
- same pathogen must be present in every case of the disease
- pathogen must be isolated from sick host and purified
- pure pathogen must cause the same disease when given to infect hosts
- pathogen must be re-isolated from newly infected hosts
name the 5 periods of disease development
- incubation period
- prodromal period
- period of illness
- period of decline
- period of convalescence
incubation period
no signs or symptoms
prodromal period
mild symptoms
period of illness
major signs & symptoms
at what period of disease development is the immune response the strongest?
period of illness
period of decline
signs & symptoms wane but highest chance of secondary infection
period of convalescence
recovery
what is epidemiology?
- study of factors and mechanisms involved in frequency and spread of diseases or other health-related problems
- used to study disease and also to design methods for control and prevention
what is prevalence and what is it used for?
- total # of people infected within a population at any given time
- used to measure strength and length of a particular disease
“streaming video”
what is incidence and what is it used for?
- number of new cases contracted within a set population in a specific period
- provides a reliable indication of the spread of a disease
“snapshot”
what is morbidity?
number of people affected by disease during a set period divided by total population
what is mortality?
number of deaths due to a specific disease during a specific period divided by total population
name 3 levels of disease occurrence
endemic
epidemic
pandemic
endemic disease
diseases found constantly within a population
epidemic disease
incidence of disease suddenly higher than expected in a specific region
name 2 types of epidemic disease
common-source
propagated
common source epidemic
- arises from contact with contaminated substances (fecal contamination of water; improperly prepared/stored food)
- affect large numbers of people but once source is identified quickly subside
propagated epidemic
- amplification of number of infected individuals as person-to-person contact occurs
- stay in population for long periods
- more difficult to control until patient zero found
pandemic
diseases that occur in epidemic proportions
name 2 types of epidemiological studies
descriptive
analytical
what are descriptive epidemiological studies concerned with?
- physical aspects of patients and spread of disease
- traces outbreak and identifies first case
what are analytical epidemiological studies concerned with?
- correlation: cause and effect hypothesis
- always uses a control group
what is often the most practical and feasible study to conduct?
observational
observational/descriptive studies
- investigator observes occurrence of condition/disease in population groups that have assigned themselves to a certain exposure
- more natural settings, representative of target pop
- little control, susceptible to distorting influences
cohort study
type of medical research used to investigate the causes of disease, establishing links between risk factors and health outcomes
prospective cohort study
- hypothesis formed about potential cause of disease
- observe a cohort of ppl over time & collect relevant data
- detect changes in health in relation to potential risk factors
disease reporting
health departments of local and state gov’t require reports of certain diseases
what are nationally notifiable diseases?
diseases that must be reported to the CDC
disease reporting pathway
healthcare providers, institutions, labs, others -> county/local -> state health departments -> CDC
what are nosocomial infections and who do they commonly affect?
- acquired in a hospital or medical facility within 48hrs of visit
- patients & healthcare workers
what area of the body is most commonly affected by nosocomial infections?
urinary tract
what is the most common nosocomial infection?
staphylococcus aureus (followed by E. coli)
nosocomial infections involve the propagation of ____
antibiotic-resistance organisms
prognosis of nosocomial infections
very poor
name 6 examples of nosocomial infections
- clostridium difficile (c. diff)
- neisseria gonorrhoeae
- carbapenum-resistant enterobacteraciae (CRE)
- vancomycin-resistant enterococcus (VRE)
- vancomycin-resistant staphylococcus aureus (VRSA)
- multi-drug resistant TB (MDRTB/XDRTB)
