Past subjects=>passed subjects=>subjects passed

October 21 2004

Epi 511

What is this? How can you use it to explain occurrence of WNV?

Host

Agent Environment

Vector

Herd Immunity

• Why is it important for vaccine programs?

• What types of “agents” work best to establish herd immunity?

• Why do you need a flu shot almost every year?

Where is the incubation period?

Exposure Infection

Observableillness

TreatmentOutcome

Pre Clinicalperiod

Clinical Period

Infectious disease

• Is the “Attack rate” more like prevalence or incidence rate?

• Give an example of primary prevention and tertiary prevention.

• Does “secondary attack rate” refer to initial disease cases becoming infected with a second disease? Explain.

• Endemic : epidemic :: usual : ?

Mortality measures

• If 4739 pedestrian vs motor vehicle deaths occurred in 2002, and there were known to be 78,000 motor vehicle accidents in that year. What is the case fatality rate?

Personalities:What did they contribute to Epi?

• John Graunt

• William Farr

• John Snow

• Joe Goldberger

• Edgar Sydenstryker

Study designs

• Describe an Ecologic study of the association between fish consumption and stroke.

• Describe a Case-control study of the association between fish consumption and stroke.

• Describe a Cohort study of the association between fish consumption and stroke.

• Describe a Randomized trial of the association between fish consumption and stroke.

Questions about designs

• Give an example of “ecologic fallacy” from the study of fish and stroke.

• Cross-sectional studies are most valuable in establishing temporal relationships, why or why not?

Disease occurrence

• How might you determine the prevalence of Parkinson’s disease in Seattle as of July 1, 2003?

• How would you determine the incidence of ALS per 100,000 population in King County, in 2003? In 1999?

• Suppose the incidence of Pancreatic ca and Multiple Sclerosis were similar, why might their prevalence be similar or dissimilar?

Standardization

• Comparing mortality rates from diarrheal disease in Somalia relative to Connecticut results in an SMR of 437. What does that mean.

• Why would we want to compute SMR?

• Is SMR most frequently associated with Direct or Indirect standardization?

Occurrence

• In Milwaukee, the proportion of deaths due to alcoholism it greater than it is in Cleveland. Therefore, persons in Milwaukee are at greater risk of death from alcoholism? Why or why not.

• MS is more prevalent in latitudes farther from the equator. Therefore your risk of MS is greater in Seattle than in L.A. Why/Why not

Rates

CIt = 1 - e -ID(t)

What does this formula calculate?Why is it useful?

Confidence intervals

• A confidence interval expresses a summary of the data in original units of measurement.

• It reflects the variability in the data, the sample size, and the actual effect size observed.

• Includes the “true” value with x% confidence• Agree or disagree with any of the above?

Why?

Design, Incidence, RR, AR?Exposed Not exposed

Subject ID #

Develop disease?

Person-years

E001 No 6.5

E002 Yes 1.5

E003 Yes 5.5

E004 No 3.5

E005 No 2.5

E006 Yes 2.0

E007 Yes 6.0

E008 No 1.5

Subject ID#

Develop disease?

Person-years

N010 No 6.5

N011 Yes 5.0

N012 No 6.5

N013 No 3.5

N014 No 4.0

N015 Yes 2.5

N016 No 6.5

N017 No 5.0