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how do viruses cause disease
- lyse infected cells
- change normal activities to make more viruses
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how do fungi cause disease
- access through inhalation or wounds
- fungal spores elease difestive enzymes to damage cells, deeper invasion
- some produce toxins
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how do protists cause disease
- destruction of cells
- interfer with host functions
- change pH (prevents enzymatic funtion and disrupts bacterial community)
- in digestive tract: blocks absorption
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how bacteria cause disease
- increase contact
- promote
- adherence
- invasion
- colonization
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bacterial exotoxins
- found in both gram + and gram -
- secreted
- predominately protein
- more specific action
- more potent
- antigenic (alisist a strong immune responce - antibiotic)
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bacterial endotoxins
- found in gram - cell wall
- lipopolysaccharides
- more stable than exotoxins (heat resistant)
- less antigenic
- less specific action
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stages in course of infectious disease
- Incubation period: no signs of symptoms
- Prodomal phase: vague symptoms. not horrible
- Invasion: most severe signs and symptoms
- Acme: worst of it
- Decline: declining signs and symtoms
- Convelescence
sizes or period of each stage/section varies
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why are dz still present with advances in medical care
- limited access to health care
- developmet of resistant strains
- new dz discovered (move into an area previously unoccupied)
- immigration and internation travel (spreads dz)
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epidemiology
the study of factors and mechanisms affecting frequency and spread of dz
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incidence
(measures of dz in population)
- number of new cases # susceptible people examined per unit time
- indicated how fast a dz is spreading
- estimated as number of new caes per 100,000 susceptible people in a target population per year
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prevalence
(measures of dz in a population)
- number of cases per number of people examined at a point in time
- estimated as number of cases per 100,000 people in a target population
- indicated how much and how long a dz affects a population
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morbiditiy rate
(measures of dz in population)
number of cases/number of people in a population/unit time
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motality rate
(measures of dz in population)
number of deaths/number of people in a population/unit of time
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endemic
always present in the population bt doesn't need to be conrolled (not worried)
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epidemic
the incidence of infection is way above what is expected
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pandemic
disease hs gone epidemic and spread worldwide
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sporadic
- disease that "pops up"
- not unexpected but we don't know when it will come up
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common source
(patterns of dz spread)
- when you have an increase over a short period of time
- food poisoning
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propagated epidemic
(patters of dz spread)
- when you get your initial case that spreads it to person ad person and so on.
- it occurs over a longer period of time with the less number of outbreaks
- common cold
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direct contact
- vertical: inutoral or suckaling
- horizontal
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indirect contact
(modes of transmission)
via formites (inantimate objects)
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(mode of transmission)
droplet
- less than or equal to 1m
- wet: breathed out in wet moisture breath
- dry: bacteria encased in mucous (outer drying protects bacteria inside -more serious - lasts longer)
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(modes of transmission)
airborne
greater than 1 m
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vehicle transmission
- waterbourne
- airborne
- food borne
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vector transmission
- mechanical: move icrobe towards you
- biological: "deer tick" get infected from another organism already infected
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reservoirs - living
- symptomatic: shoes symptoms
- carriers: not showing symptoms
- zoonotic: animals
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reservoirs - nonliving
- ground, soil, or dirt
- ringworm -- fungus
- endospores
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factors associated with nosocomial infections
- invasive procedures
- compomised hosts -- wounds, immune suppressed
- concentration of microbes
- antibiotic resistance
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