Synthesis – Foodborne Outbreaks

EPIET Introductory Course, 2006Lazareto, Menorca

Prepared by: Mike Catchpole

Steps of an outbreak investigation

• Confirm outbreak and diagnosis• Form Outbreak Control Team• Define a case • Identify cases and obtain information• Describe data by time, place, person• Develop hypothesis• Test hypothesis: analytical studies • Additional studies• Communicate results:

– outbreak report, publication• Implement control measures

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Epidemiological findings

• Descriptive data– Who was affected, when and where

• Analytical studies– May demonstrate statistically significant

association between illness and particular demographic or exposure variables

But...

But...

• Why?

• How?

• Where from?

• How can we stop it happening (again)?

Foodborne outbreaks: most common causes in UK

• Preparation of food too far in advance of needs• Storage of food at room temperature• Inadequate cooling• Inadequate reheating• Use of contaminated processed food• Undercooking • Cross contamination from raw to cooked food• Consumption of raw food• Infected food handlers

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Routes of Food Contamination • Contamination of raw food or failure to eliminate “acceptable”

contamination of raw food– Farming practice/abattoir practice/zoonotic problems– Pasteurisation failure– Undercooking, inadequate cooling

• Contamination during food preparation– Infected food handler– Environmental contamination– Cross contamination (from raw or processed ingredients)

• Contamination after food preparation– Infected food handler– Inadequate storage, cooling or reheating– Environmental contamination– Cross contamination from raw food

Identifying the cause of food contamination

• Inspection and microbiological examination of food preparation premises– Questioning about food preparation staff health– Observation and questioning about food

preparation practices (storage of raw/cooked foods)

– Scrutiny of records (staff sickness, fridge/freezer temperature charts, oven temperature charts, cleaning records) and checking of calibration of instruments

Identifying the cause of food contamination

• Inspection and microbiological examination of farms – Scrutiny of records (pasteurisation temperature

charts, veterinary records, staff sickness records) and checking of calibration of instruments

– Observation and questioning about animal husbandry and crop management

Identifying the cause of food contamination

• Inspection and microbiological examination of commercial food preparation premises and “track back” of food distribution chains– Scrutiny of records (temperature charts, quality

control records, staff sickness records) and checking of calibration of instruments

– HACCP (hazard analysis of critical control points) and inspection of production line

– Inspection of supplier records

Why investigate outbreaks?

• Stop the outbreak• Understand what happened and why• Prevent future outbreaks• Improve our knowledge• Improve surveillance and outbreak detection

• Training