Investigation of Foodbourne Outbreaks

Question 1

What is the difference between an outbreak and a sporadic case of foodbourne illness?

Answer 1

An outbreak is made up of 2 cases from the same source. A sporadic case is made up on 1 case.

Question 2

Describe how PFGE is performed.

Answer 2

PFGE uses restriction enzymes to cut DNA in specified sites. Depending on the DNA different amounts of cuts will be made. the cuts create a unique pattern for a DNA sequence that can be run on an agarose gel to visualize and compare the pattern. Also see slides 12-15.

Question 3

Describe how an odds ratio is calculated.

Answer 3

See slides 19-20. 19 is a good explanation and 20 is an example.

Question 4

What is the difference between molecular and traditional epidemiology?

Answer 4

Molecular epidemiology uses DNA techniques like PFGE and traditional epidemiology uses interview techniques and odds ratios.

Question 5

True/False: The process of identifying an outbreak always follows the same sequence of steps.

Answer 5

False. Outbreaks do not always follow a clear cut path. Refer to the arrows on slide 3 for a visual.

Question 6

What is a cluster, and how is informal and formal reporting used to identify a cluster?

Answer 6

Slide 6 discusses these issues.

Question 7

When role do local, state, and the Centers for Disease Control play when it comes to investigating an outbreak?

Answer 7

Slide 5 talks discusses how the severity and range of an outbreak dictates who gets involved.

Question 8

How is an epidemic (epi) curve used to track outbreaks?

Answer 8

See discussion from slide 7

Question 9

What is PulseNet, and what role do they play in investigating outbreaks?

Answer 9

PulseNet is the international organization that serves as a repository for PFGE information, and looks to see if organisms with the same PFGE pattern are appearing at a much higher frequency than expected; see slide 16

Question 10

What is meant by a “case definition”? How does the establishment of a case definition assist with an outbreak investigation?

Answer 10

See slide 17

Question 11

What are three shortcomings/considerations when using food surveys during an outbreak investigation?

Answer 11

See slide 20 for discussion of food recall, co-linear foods, and matched case control studies.

Question 12

After an outbreak has been controlled and is determined to be “over”, what steps follow?

Answer 12

Remember from slide 25, that investigations into understanding how and why the outbreak occurred are crucial.