outbreak investigation Flashcards
what is an endemic ?
defined as the habitual presence of a disease within a given geaographical area
what is an epidemic ?
occurence in a community or region of a group of illnesses
what is a pandemic ?
refers to a worldwide epidemic
what is an outbreak ?
occurence of more cases of disease than expected in a specific place and time in a specific group of people
what is a cluster ?
an aggregation of cases
what factors may change a cluster to become an outbreak ?
person
place
time
how can an outbreak be detected ?
health personnel
laboratories
newspaper and media
concerned citizens
what are the steps of outbreak investigations ?
- confirm the existence of an outbreak
- verify diagnosis and etiology of the disease
- case definition and case finding
- describe person, place and time, formulate hypothesis
- test hypothesis
- carry out additional studies to support epidemiological study
- draw conclusions
- provide preventative protocol and report
- communicate the findings to educate people
- follow up the recommendations
when can outbreak be declared ?
detection of a single case in a non endemic area
or
after the number of reported cases reaches the threshold incidence rate
what are factors that may affect the reporting of the number of cases ?
diagnostic bias
diagnostic errors
seasonal variations
notification artefacts
what are the factors that affect the decision to launch a field investigation ?
severity of the illness the transmissibility ongoing illness availability of control measures political considerations
what is the best next step in action once an outbreak has been confirmed ?
further investigations
what is case definition ?
a standard set of criteria for deciding whether a person should be classified as having the illness or not
what are the different degrees in certainty when it comes to case definiton ?
suspect
probable
confirmed
what is the gold standard to diagnose a specific disease ?
the case definition
what is the general rule for case finding and case definition ?
cast the net wide and get all the fish
what are the different types of surveillance ?
active
passive
sentinel
syndromic
what is a line listing ?
a list of possible cases based on information collected
what points are to be addressed in the descriptive epidemiology part ?
time
person
place
how is the scourse of an epidemic presented ?
through an epidemic curve
what does the epidemic curve provide information on ?
the course of the epidemic
if the incubation period is known
what are the different types of epidemic curves ?
point source outbreaks
continuous common source epidemic
propagated epidemic curve ( person to person)
what are the features of common source outbreak ?
lasts more than one incubation period
cases dont all Happen in one incubation period
what is a propagated epidemic curve ?
infectious agent is propagated in a community by passage from person to person
what are the main features of a propagated curve ?
rises and falls gradually
cases occur over a longer period of time (more than one incubation period )
what is an example of a common source epidemic ?
cholera
what is an example of a propagated source ?
secondary and tertiary cases ( hepatitis A)
when describing the place of which an outbreak happened which rate should be used ?
attack rate
what are the two ways of evaluating a hypothesis ?
analytical epidemiology
comparison of the hypothesis with established facts
what is the purpose of analytical epidemiology ?
use a comparison group top quantify relationships
what is the purpose of comparing the hypothesis with established facts ?
evidence is so strong that the hypothesis does not need to be tested
what kind of studies can we use to test a hypothesis ?
case control
cohort
what is the formula for the attack rate ?
number of people who got sick
_____________
no of people who are at risk
how would the overall attack rate be calculated ?
number of new cases
______________
total population
what is the excess risk ?
the attributable risk
how is the attributable risk calculated ?
incidence in exposed - incidence in unexposed
___________________
incidence in exposed
what is the difference in population between cohort and case control studies ?
in cohort - it is a well defined population
case control - not in a well defined population
what is the comparitive measure in cohort and in case control ?
cohort - compares rate of illness among those with risk factors and those without
case-control - compares exposure among people with illness and those without illness
what are the measurement of association a cohort study ?
incidence
relative risk
attributable risk
what are the measurements of association in a case control study ?
odds ratio
proportion of exposure
what is the primary goal in outbreak investigations ?
control of the outbreak and prevent occurence of additional cases
when should control measures be done ?
at any time during the outbreak investigation
when can we say that an outbreak has ended ?
when the number of new illness drops back to the normally expected
