Basic Epi Flashcards
epidemiology
study of distribution and determinants of health or disease in a population, and application of this study to control health problems
it is a young science!
objectives of epi
- determine etiology or cause of disease + risk factors that increase risk
- determine extent of disease in community
- study natural history and prognosis of disease
- evaluate existing and new preventive and therapeutic measures and modes of healthcare delivery
- provide foundation for public policy and decisions on environmental problems
3 types of prevention
- primary
- secondary
- tertiary
primary prevention
prevent initial development
EX: immunization, limit exposure to risk factor
secondary prevention
early detection of existing disease to reduce severity and complications
EX: screen for cancer
tertiary prevention
reduce impact of disease
EX: rehab for stroke
surveillance
ongoing, systematic collection, analysis, and interpretation of data essential to planning, implementing and evaluating public health practices, and dissemination of info
what is surveillance useful for
identify changes in disease
planning
help identify risk factors
surveillance methods
passive
active
sentinel
passive surveillance
data from doctors, labs, hospitals
cheap, but may have underreporting
active surveillance
data actively collected during outbreaks by surveys and medical professionals
expensive and labor intenstive
sentinel surveillance
early warning system by focused activities on early detection
cheap and fast, but only works for some diseases
prevalence
disease burden
number of cases in pop. at point / period of time
accounts for duration
snapshot of time
prevalence =
incidence x duration
duration includes
death and cure rate
incidence
disease risk
new case / ppl at risk x 1000
measures risk or probability individual will get disease in a given period of time
confounding
other risk factors that impact disease
how can we control for confounders
in data analysis
in study design
bias
any systematic error in design, conduct, or analysis that results in mistake estimate of exposure’s effect on risk of disease
endemic
natural/normal occurrence of disease in certain area
EX: malaria in Africa
epidemic
occurrence of disease beyond what is expected or considered normal (must measure normal)
EX: smallpox, measles, polio
pandemic
epidemic that occurs over wide area
EX: global flu, AIDS, COVID-19
if disease occurrence is greater than epidemic level, we investigate
who was attacked (sex, age race)
when did it occur (season, trends overtime)
where did cause arise (clusters? EX: Lyme disease, West Nile Virus, COVID-19)
infectious disease 2 types of transmission
direct and indirect transmission
direct infectious disease transmission
physical contact, touch, sex, droplets
indirect infectious disease transmission
contaminated surfaces/objects:
air, water, food
vectors: mosquitoes, flies, ticks, pests
basic reproduction number
R0
R0 describes
contagiousness of infectious agents
OR
number of secondary cases 1 case would produce in a completely susceptible population
3 parameters for R0
- duration of contagiousness after a person is infected
- likelihood of infection per contact btwn. susceptible and infectious person
- contact rate
R0 only applies when…
everyone in population is completely vulnerable
what is required for whole population to be vulnerable
no one has been vaccinates
no one had disease before
there’s no way to control spread of disease
R0 is NOT:
a biological constant, a rate over time, or a measure of severity
can R0 measure severity?
no!
incubation period
internal from receipt of infection to time of onset of clinical illness
carrier status
individual harbors organism, but isn’t infected by symptoms or serologic studies
CAN infect others
EX: Typhoid Mary (chef infected others for years)
herd immunity
resistance of a group to an attack by a disease to which a large proportion of group are immune (EX: polio)
