How do plagues spread? Flashcards
how do religion and taboo influence ideas of disease and vice versa?
rise of large contemporary religions occurred during rise of cities, potentially during times of plague.
food prohibitions may have developed as strategy for reducing risk of pathogen exposure.
ex. pork is not kosher or halal- tricinosis are worms found in pork muscle and can’t be cooked out.
there is a strong correlation between disease richness and number of religions in an area
the humoral theory of disease
incorrect balancing of humours led to disease
no understanding of infection
blood, phlegm, black bile and yellow bile
miasma theory of disease
bad air causes disease
bad smells
how did the scientific revolution change the theories surrounding disease?
Robert Koch stressed disease specificity: where one microorganism causes one disease
framework- the pathogen as the disease causing agent
describe the germ theory of disease
microorganisms/pathogens/germs cause disease. these small microorganisms are too small to be seen without magnification. they can invade humans, other animals and other living hosts. their growth and reproduction within their hosts can cause disease.
Contributions made by Pasteur, Lister and Koch
Louis Pasteur contributions
shows existence of microorganisms, thus demonstrating the utility of germ theory
Joseph Lister contributions
applied Pasteur’s microbiology to produce antiseptics and discredit the idea of miasma causing infectious disease
Robert Koch contributions
discovered cholera bacteria
Koch’s Postulates
What are Koch’s Postulates?
- the microorganism must be found in abundance in all organisms with the disease but should not be found in healthy organisms
- the microorganism must be isolated from a diseased organism and grown in pure culture
- the cultured microorganism should cause disease when introduced into a healthy organism
- the microorganism must be re-isolated from the inoculated, diseased experimental host and identified as being identical to specific causative agent
Who is the father of epidemiology?
John Snow
mapped the london cholera outbreak of 1848
what is epidemiology
the study of patterns, causes, and effects of health and disease conditions in defined populations
pathogen
anything that produces disease
microorganism
living creatures (plant or animal) visible with a microscope
microscopic
invisible to the eye
macroscopic
visible without a microscope
symbiotic relationship
microorganism and host benefit
commensal relationship
one benefits without damaging the other
parasitic relationship
one befits at other’s expense
what sort of relationship is seen in disease?
parasitism, or commensalism gone wrong
types of pathogenic microorganisms
bacteria
virus
fungi
protozoa
bacteria
single celled fast growing organisms
shapes of bacteria
coccus= sphere
bacillus = rod
vibrio = curved
spirillum and spirochetre = spiral
strepto__ = chain of ____
true or false: most bacteria are pathogens
false
carrier state
appearance of an organism of relatively high pathogenicity in the normal flora without causing disease
how can bacterial disease come about?
some bacteria are entirely adapted to be pathogens and never occur in normal flora (TB, plague)
some bacteria are part of normal flora that become virulent and pathogenic (E.Coli)
some bacteria from normal flora cause disease if they gain access to deep tissues
immunocompromised patients, normal flora causes disease especially in deep tissues
viruses
microscopic organisms that can infect hosts
small pieces of genetic information inside a capsid shell or envelope.
cant reproduce without a host
viruses are smaller than bacteria
have no nucleus or cell wall
have a simpler genome
antibiotics DO NOT WORK
which of the following is enveloped: bacteriophage or influenza
influenza
fungi
yeasts and molds
relatively few fungal diseases are pathogenic to humans
protozoa
single celled with complex life cycle, many stages
what species is greatest source of infection for humans?
humans
modes of direct transmission
direct contact
respiratory
fecal-oral
sexual contact
forties
direct contact transmission
direct person-person contact
contact with contaminated skin (hands), saliva, respiratory secretions, blood
respiratory transmission
spread through droplets and inhaled via coughing, sneezing, laughing, and close contact
aerosols within + beyond 1m
droplets less than 1m
fecal oral
germs found in feces of infected person are spread to another person
person touches stool of infected person, or ingests something contaminated with infected feces
sexual contact transmission
STIs can be bacteria, viruses or parasites
may pass through blood, semen, vaginal or other bodily fluids
fomites transmission
non living object that transmits disease
door handles, phones, desktops, buttons
zoonosis
an infectious disease transmitted to humans from non human reservoir
there are often “spillover” infections. which are incidental infections that fail to produce sustained epidemics in new hosts
reservoir host: natural host in which pathogen is endemic or epidemic
host jumping
when an infectious disease causes sustained infection in a novel host species
emerging disease
an infectious disease whose incidence has increased precipitously in recent past
vector
any intermediary agent that passes pathogens to another individual
zoonosis stages
- animal only: microbe present in animals has not been found in humans
- primary infection: pathogen that under natural conditions can be transmitted from animal to human but not transmitted between humans (ex. rabies)
- limited outbreak: animal pathogen can undergo few cycles of secondary transmission in humans, but occasional human outbreaks eventually die out
- long outbreak: disease exists in animals, and can also infect humans by primary transition form animal host, and has long sequences of secondary transmission between humans without need of animal hosts
- exclusive human agent: pathogen exclusive to humans
what 3 things control disease emergence? describe them
ecological factors
- proximity of donor and recipient populations
-size/density of donor and recipient populations
genetic factors
- effectiveness of immune response in clearing pathogen
- ability to recognize and replicate in host cells
- variation and adaptability to pathogens
overall patterns
- generally, cross species transmissions are less likely among phylogenetically divergent hosts
- most cases of emergence are spillovers with no onward transmission
