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Flashcards in Epidemiology Deck (49)
1

Epidemiology definition

study of cause, development and transmission in the human population

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2 approaches to epidemiology

1. retrospective
2. prospective

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retrospective epidemiology

look back from outbreak to source

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John Snow

traced cholera outbreak to fecal contamination

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Florence Nightingale

traced typhus to lice

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Semmelweiss

traced uterine infection to doctors handling cadavers before delivering babies

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prostpective epidemiology

try to predict, recognize, prevent or remove conditions before disease can occur

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4 disease transmission patterns

1. pandemic
2. epidemic
3. endemic
4. sporadic

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pandemic

world wide effects, more than one continent
AIDS, flu

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epidemic

widespread illness with increasing transmission
polio, Chlamydia

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endemic

illness always present
chicken pox, Lyme disease, Histoplasmosis, cholera

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sporadic

cases occur occasionally in different locations
tetanus in US

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5 stages of disease development

1. incubation
2. prodromal period
3. illness
4. decline
5. convalensce

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incubation

time between infection and onset of symptoms

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incubation time variables

1. type of pathogen
2. virulence of agent
3. inefective dose
4. health of immune system
5. infection site

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prodromal period

onset of mild disease symptoms

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illness

display of classic symptoms of disease
immune system has not fully responded

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decline

typical symptoms of disease decrease
pathogen declines

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convalescence

period of recovery

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two patterns of infection

acute
chronic

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3 disease prevention techniques

1. reduce, remove or prevent contact with reservoirs
2. prevent or reduce transmission of pathogens
3. immunization of population

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3 reservoirs

1. humans
2. animals
3. non-living

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zoonosis

transmission from animals to humans

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non living reservoir examples

soil, water, milk

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person to person transmission

1. directly from person to person
2. indirect by fomites, water, food, air
3. respiratory droplets- exhales, sneeze, cough
4. vectors

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fomites

inanimate object that carries disease-causing organisms

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prevention efforts to prevent person to person transmission

1. hand washing
2. clean drinking water
3. clean food
4. insect control
5. improved nutrition
only airborne pathogens are unavoidable

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two types of immunization

active
passive

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active immunizations

antigens stimulate immune syster to produce antibodies and produce memory

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antigen

surface characteristic of agent

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antibodies

produced by immune system against the antigen

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immunogenic vaccines

provide immunity without causing disease
MMR, polio, HiB

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herd immunity

artificially make population immune to disease by reducing the number of susceptible hosts

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attenuated vaccines

live vaccines
the pathogen continues dividing
stimulates the immune system but does not cause disease
long lasting/ lifelong immunity

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attenuated vaccine disadvantage

may be transmitted to immune compromised individuals
can mutate back to virulent forms and cause disease

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inactivated/killed vaccines

antigen property remains intact but cannot replicate
stimulates antibody production but requires larger doses or boosters

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subunit vaccines

chemically, genetically engineered antigen that stimulates the immune system
cannot replicate- requires boosters
tetanus toxoid

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altered exotoxin

antibodies produced against toxin
requires boosters every 10 years
stimulates antibody producing memory cells
hepititis B, diphtheria toxoid, anthrax vaccines

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passive vaccines

do not stimulate immune system to produce antibodies
no antigen characteristics
donor antibodies injected into infected individual
immediate response to toxin or pathogen
short duration, no memory

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gammaglobulin

injection or preformed, mostly IgG antibodies from other individuals

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varicella zoster globulin

passive immunity against chickenpox and shingles

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passive immunization disadvantage

no memory of exposure
preformed antibodies degraded over time
possible allergic reactions to animal produced antibodies (serum sickness)

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vaccine side effects

contamination
mutation to virulent or pathogenic forms
suspected cause of autism, asthma, allergies

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tetanus toxoid globulin vaccine

combines active and passive
toxoid- active
globulin- passive

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nosocomial infections

hospital acquired infections

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secondary infections

not present at time of admission

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3 factors contributing to hospital acquired infections

patient condition
mode of pathogen transmission
bacteria always present in hospital environment

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MRSA

methycillin resistant Staphylococcus aureus

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nosocomial infection examples

UTIs (most common)
pneumonias
skin infections- Staph aureus (diaper rash)
Pseudomonas aeriginosa (burns)