Lecture 32 - Outbreak Investigation

Question 1

Infectious Disease Epidemiology

Answer 1

• distribution (who, where, when)
• determinants (risk factors or exposures)
• *looking at entire population**

-Triad (host –> infectious agent –> environment) is there a vector that connects the three

Question 2

Modes of Transmission

Answer 2

• Direct

- Indirect

Question 3

Direct Transmission

Answer 3

• person to person

- respiratory droplet (flu), contact (scabies)

Question 4

Indirect Transmisison

Answer 4

• common vehicle
• air (tuberculosis), water (cryptosporidiosis), or food (e.coli)
• vector
• insects (malaria, chikungunya, west nile), animals (bats/dogs and rabies)

Question 5

Defining an Outbreak

Answer 5

• increase in incidence of event over expected rates
• new cases/population at risk

-definition depends on the type of outbreak and the setting (ex. 3 or more cases of a disease that is not a food-borne illness and that occurs in individuals that are not living in the same household, but who are epidemiologically linked)

Question 6

Endemic

Answer 6

a disease that exists permanently in a particular region or population. Malaria is a constant worry in parts of Africa

Question 7

Epidemic

Answer 7

An outbreak of disease that attacks many peoples at about the same time and may spread through one or several communities.

Question 8

Pandemic

Answer 8

When an epidemic spreads throughout the world.

Question 9

Developing a Case Definition:

Answer 9

• numerator = the ppl with your disease/condition of interest
• the case definition should specify the clinical syndrome of interest with restrictions to time, place, and person

Question 10

Probable Case vs. Confirmed Case

Answer 10

• a probable case has the symptoms but no lab values

- a confirmed case has both symptoms and lab values

Question 11

Sensitivity

Answer 11

-the ability of case definition to correctly identify those that have the infection

A-true (+) B- false (+)
C- false (-) D- true (-)

A/A+C x 100

Question 12

Specificity

Answer 12

-the ability of the case definition to correctly identify those without the disease

A-true (+) B- false (+)
C- false (-) D- true (-)

D/D+B x 100

Question 13

PPV - Positive Predictive Value

Answer 13

A-true (+) B- false (+)
C- false (-) D- true (-)

A/A+B x 100

Question 14

Outbreak Investigation Steps

Answer 14

• prevent further cases
• develop a case definition
• conduct surveillance for case patients
• build and interpret an epidemic curve
• summarize data on case patients in a line listing
• develop and test hypothesis of what caused the outbreak
• prevent further outbreaks