Case definitions, populations at risk, and reading graphs

What are the phases of an outbreak investigation

• describe it

• collect and analyze data

• implement control

• follow up

• communicate

Do the phases of an outbreak investigation all occur in in the same order

no

What 2 things do you need to determine if you have an outbreak

• case definition

• confirmation that the case meets the definition

Once you’ve determined the case definition you can quantify an outbreak in two ways what are they?

• one case is enough

• compare the number

One case is enough is considered an outbreak if they have ___________ in population before

never been present

What is an example where one case would be considered an outbreak

regulatory diseases

Another way to determine an outbreak is through comparing the numbers what 4 sources could you pull from to compare?

• facility surveillance

• analysis of records

• national/international surveillance

• published literature

What things are necessary to know to detect change

• # of cases

• population at risk

• agent causing disease

• details of the case

How would you calculate the attack risk of an outbreak

cases/populaiton at risk

How would you calculate the morbidity of an outbreak

sick cases/populaiton at risk

how would you calculate the case fatality rate of an outbreak

dead cases/cases

Who is considered the population at risk?

those who could have gotten the disease

All cases must be members of what?

The population at risk

What are the patterns in an epidemic curve

• point source

• propagated

• sporadic

What are the patterns in the endemic curves?

• variation around constant

• seasonal

When evaluating a point source epidemic curve you should calculate what?

Attack risk

when evaluating a propagating epidemic curve you should use what?

Traces

How can you calculate the attack risk ratio

attack risk of expose/attack risk of not exposed

When trying to gather data to calculate Attack risk ratio’s what study design would you use when the source is unknown

• case control studies

• cross sectional studies

When trying to gather data to calculate Attack risk ratio’s what study design would you use when the source is known

cohort studies

is the study population the same as the population at risk?

no

What is needed to determine the source?

• High ARR

• plausibility

• temporality

High ARR does not always indicate increased risk of contraction it can indicate increased risk of __________

spread