Epidemic Investigation Flashcards
The unusual occurrence in a community of disease, specific health related behavior, or other health related events clearly in EXCESS of expected occurrence
Epidemic
t/f Epidemics can occur upon endemic states too
true
usually limited to a small focal area
Outbreak
covers larger geographical areas & has more than one focal point.
Epidemic
It refers to the constant presence of a disease or infectious agent within a given geographic area or population group.
> It is the usual or expected frequency of DISEASE WITHIN A POPULATION
Endemic
disease is constantly present at high incidence and/or prevalence rate and affects all age groups equally.
hyperendemic
high level of infection beginning early in life and affecting most of the child population, leading to a state of equilibrium such that the adult population shows evidence of the disease much less commonly than do the children (e.g. malaria)
holoendemic
An epidemic usually affecting a large proportion of the population, occuring over a wide geographic area such as a section of a nation, the entire nation, a continent or the world, e.g. Influenza pandemics
Pandemic
imported into a country in which they do not otherwise occur, as for example, rabies in the UK.
Exotic diseases
scattered about
Sporadic
an infection that is transmissible under natural conditions from vertebrate animals to man
Zoonosis
an outbreak (epidemic) of disease in an animal population, e.g. rift valley fever.
Epizootic
endemic occurring in animals, e.g. bovine TB
Enzootic
an outbreak occur in a group of people eating food contaminated with microorganisms
COMMON-VEHICLE OUTBREAK
TYPES OF EXPOSURES
Single exposure
Multiple exposure
Periodic exposure
Continuous exposure
A contaminated food is served only once resulting in single exposure to people who eat it
Single Exposure
Food served more than once, resulting to multiple exposures to people who eat it more than once
Multiple exposure
A water supply contaminated with sewage because of leaky pipes
Periodic Exposure
Cause multiple exposures causing intermittent contamination
Periodic exposure
Constant leak leads to persistent contamination
Continuous Exposure
there is rapid increase in no. of cases of a disease in a population
Explosive
the first wave of cases would not expect the disease to develop in people who were not exposed… Unless there are other affected of the disease in the community
Self-evident
t/f In food-borne outbreak, cases rarely occur in persons who acquire it from primary case
T
Number of people at risk in whom a certain illness develops
Attack Rate
Determinants of disease development
Risk Factor
graphical depiction of the number of cases of illness by the date of illness onset
epidemic curve
The overall shape of the epi curve can reveal the type of outbreak
Common source
Point source
Propagated
Outbreak Pattern of Spread
> P eople are exposed continuously or intermittently to a harmful source
Period of exposure may be brief or long
Intermittent exposure often results in an epi curve with irregular peaks that reflect the timing and the extent of exposure
Continuous exposure will often cause cases to rise gradually (and possibly to plateau, rather than to peak)
Common Source
Typically shows a sharp upward slope and a gradual downward slope
Point Source
Is a common source outbreak in which the period of exposure is brief, and all cases occur within one incubation period
Point Source
Is spread from person to person
Can last longer than common source
Propagated
has progressively taller peaks, an incubation period apart
Propagated Outbreak
Can provide a sense of the magnitude of an outbreak
Epidemic Curve
Allow information about the time trend of the outbreak to be gleaned
Outbreak Time Trend
If the timing of the exposure is known, epi curves can be used to estimate the incubation period of the disease
The time between the exposure and the peak of the epi curve represents the median incubation period
Incubation Period for the Outbreak
Plot the number of cases of disease reported during an outbreak on the
Y- AXIS
Plot the time or date of illness onset
X-AXIS
There should not be any space between the x-axis categories
HISTOGRAMS
Cases where answers are not obvious and further support is needed to decide evaluate the relationship between risk factors and causation
analytical epidemiology
Both of these studies make use of a comparison group to quantify relationship between exposure and disease
case-control study
prospective cohort study
attack rate exposed group
attack rate unexposed group
Compute for relative risk
(+) values for incidence of disease in exposed and non-exposed group
Cohort
% of cases exposed (diseased)
% of controls exposed (non diseased)
We do not know the incidence of disease in both exposed and non-exposed group
Compute for the odds ratio
Case control
