Epidemiology Flashcards
Epidemiology definition
study of cause, development and transmission in the human population
2 approaches to epidemiology
- retrospective
2. prospective
retrospective epidemiology
look back from outbreak to source
John Snow
traced cholera outbreak to fecal contamination
Florence Nightingale
traced typhus to lice
Semmelweiss
traced uterine infection to doctors handling cadavers before delivering babies
prostpective epidemiology
try to predict, recognize, prevent or remove conditions before disease can occur
4 disease transmission patterns
- pandemic
- epidemic
- endemic
- sporadic
pandemic
world wide effects, more than one continent
AIDS, flu
epidemic
widespread illness with increasing transmission
polio, Chlamydia
endemic
illness always present
chicken pox, Lyme disease, Histoplasmosis, cholera
sporadic
cases occur occasionally in different locations
tetanus in US
5 stages of disease development
- incubation
- prodromal period
- illness
- decline
- convalensce
incubation
time between infection and onset of symptoms
incubation time variables
- type of pathogen
- virulence of agent
- inefective dose
- health of immune system
- infection site
prodromal period
onset of mild disease symptoms
illness
display of classic symptoms of disease
immune system has not fully responded
decline
typical symptoms of disease decrease
pathogen declines
convalescence
period of recovery
two patterns of infection
acute
chronic
3 disease prevention techniques
- reduce, remove or prevent contact with reservoirs
- prevent or reduce transmission of pathogens
- immunization of population
3 reservoirs
- humans
- animals
- non-living
zoonosis
transmission from animals to humans
non living reservoir examples
soil, water, milk
person to person transmission
- directly from person to person
- indirect by fomites, water, food, air
- respiratory droplets- exhales, sneeze, cough
- vectors
fomites
inanimate object that carries disease-causing organisms
prevention efforts to prevent person to person transmission
- hand washing
- clean drinking water
- clean food
- insect control
- improved nutrition
only airborne pathogens are unavoidable
two types of immunization
active
passive
active immunizations
antigens stimulate immune syster to produce antibodies and produce memory
antigen
surface characteristic of agent
antibodies
produced by immune system against the antigen
immunogenic vaccines
provide immunity without causing disease
MMR, polio, HiB
herd immunity
artificially make population immune to disease by reducing the number of susceptible hosts
attenuated vaccines
live vaccines
the pathogen continues dividing
stimulates the immune system but does not cause disease
long lasting/ lifelong immunity
attenuated vaccine disadvantage
may be transmitted to immune compromised individuals
can mutate back to virulent forms and cause disease
inactivated/killed vaccines
antigen property remains intact but cannot replicate
stimulates antibody production but requires larger doses or boosters
subunit vaccines
chemically, genetically engineered antigen that stimulates the immune system
cannot replicate- requires boosters
tetanus toxoid
altered exotoxin
antibodies produced against toxin
requires boosters every 10 years
stimulates antibody producing memory cells
hepititis B, diphtheria toxoid, anthrax vaccines
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
gammaglobulin
injection or preformed, mostly IgG antibodies from other individuals
varicella zoster globulin
passive immunity against chickenpox and shingles
passive immunization disadvantage
no memory of exposure
preformed antibodies degraded over time
possible allergic reactions to animal produced antibodies (serum sickness)
vaccine side effects
contamination
mutation to virulent or pathogenic forms
suspected cause of autism, asthma, allergies
tetanus toxoid globulin vaccine
combines active and passive
toxoid- active
globulin- passive
nosocomial infections
hospital acquired infections
secondary infections
not present at time of admission
3 factors contributing to hospital acquired infections
patient condition
mode of pathogen transmission
bacteria always present in hospital environment
MRSA
methycillin resistant Staphylococcus aureus
nosocomial infection examples
UTIs (most common)
pneumonias
skin infections- Staph aureus (diaper rash)
Pseudomonas aeriginosa (burns)
