CS: foodborne outbreak investigation

Question 1

Define attack rate

Answer 1

= # new cases in population at risk / # persons at risk in the population

Question 2

What is a hold and test protocol?

Answer 2

Instigated by FSA at a food seller: can’t sell any more (ice cream) until negative culture for bacteria

Question 3

Which organisation would be involved in informing GPs/hospitals etc of the confirmation of a foodborne outbreak?

Answer 3

Public Health England (PHE)

Question 4

Typical incubation period for Listeria

Answer 4

3-70 days (makes investigation tricky d/t wide range)

Question 5

How big is >1000 CFU/ gram of food?

Answer 5

quite a high infective dose

Question 6

T/F: growth of pathogen in food is not necessary to cause disease

Answer 6

True

Question 7

Is it worth screening dairy animals for management of listeria?

Answer 7

No - environmental source possible so testing animals wouldn’t be enough. Also having listeria negative aniamls wouldn’t always mean you have a listeria free status

Question 8

Sources - listeria

Answer 8

• biofilms on drains, floor, stainless steel
• animal (cows can be subclinical carriers)
• muddy and dusty environment of farm ideal
• pooled water and cool environment ideal (processing plants)