1environmental health investigation module 4 – environmental health investigation foodborne...
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1Environmental health investigation
Module 4 – Environmental Health Investigation
Foodborne Disease Outbreak Investigation Team Training:
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Module Learning ObjectivesAt the end of this module, you will be able to
1. Discuss how contributing factors are related to the causative agent, suspect food, and food processing method.
2. Compare an environmental health assessment with a HAACP plan review, facility plan review, and regulatory inspection.
3. List types of activities included in an environmental health assessment.
4. Describe the likely role of local jurisdictions in a traceback investigation.
> Learning objectives
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Food System
Primary producers
Manufacturers
Distributors
Retailers
Point of service establishments
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Food Establishments as Dynamic Systems
INPUTS: - Raw foods- Ingredients- Chemicals- Packing materials- Water
Receive
StorePrep
Cook
Cool
Reheat
Hold Assemble
Package
Store
Serve
OUTPUT: Final product
Underlying Factors
Foods and their properties
Food workers
Equipment
Processes
Policies
Management
Economics
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Contributing Factors
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Contributing Factors
• Factors that increase the risk of foodborne illnesses and repeatedly contribute to outbreaks
• Identification (and correction) of these factors facilitates prevention and control of foodborne diseases
• Three major categories– Contamination– Survival– Proliferation
> Contributing factors
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Contamination Survival Proliferation
Natural toxinAdded poisonous
substanceToxic containerContaminated food
eaten raw or lightly cooked
Unsafe sourcesCross-contaminationInfected food workerUnclean equipmentPoor storage
practices
Improper cooking or heat processing
Improper reheatingInadequate
acidificationInsufficient thawing followed by insufficient cooking
Categories of Contributing Factors
Improper refrigerationPreparation too far in
advance of servingProlonged cold storageImproper hot-holdingInsufficient acidificationInsufficiently low water
activityInadequate thawing of
frozen foodsAnaerobic packagingInadequate
fermentation
> Contributing factors
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Contributing Factors
• Presence alone may not be sufficient to cause illness
• A relationship exists between contributing factors, food vehicle, causative agent, and processing methods
> Contributing factors
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Common Contributing Factors by Causative Agent and Food
Situational Keys A-F (starting on page 80)
> Contributing factors
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Generalizations
Causative agent
Common contributing factors
Spore formers andpreformed toxins
Cooling, reheating, hot holding, bare- hand contact, room temperature storage, cold holding
Viral infections Ill food worker, bare-hand contact, inadequate handwashing, contaminated raw products, contaminated surfaces
Bacterial infections Ill food worker, bare-hand contact, inadequate handwashing, contaminated raw product, cross-contamination, inadequate cooking
Parasitic infections Contaminated raw products, source, water, cross-contamination, inadequate cooking > Contributing factors
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Class QuestionAre the following likely to be contributing factors for the outbreaks described?
Bare-hand contact of lettuce in an out- break of shigellosis linked to a salad bar
Refrigerator at 47 in an outbreak of hepatitis A virus linked to a restaurant
Refrigerator at 47 in an outbreak of Staphylococcal intoxication linked to potato salad
Cat in the kitchen of a restaurant prior to an outbreak of norovirus
> Contributing factors
Contributing factor
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Environmental Antecedents
• The root cause or circumstances that set the stage for contributing factors to occur
• Include economic constraints, inadequate worker education, management decisions, social and cultural beliefs
• Must be addressed to eliminate contributing factors
> Contributing factors
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Example
• Salmonellosis outbreak linked to potato salad• Contributing factor: Potato salad contaminated
because placed under thawing chicken in refrigerator
• Environmental antecedents: Economic issues led to hiring more part-time workers who were less experienced, inadequate food worker education, inadequate oversight and supervision
> Contributing factors
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“When you have a foodborne outbreak, more than one thing
went wrong.”
Dr. Frank Bryan
> Contributing factors
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Environmental Health Assessment
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Environmental Health Assessment
• A systematic, detailed, science-based evaluation• Focuses on factors that contributed to an
outbreak • Different from a
– Hazard Analysis and Critical Control Point (HACCP) risk assessment review
– Facility plan review – Food establishment regulatory inspection
> Env’t health assessment
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HACCP Risk Assessment Review• Preemptive solutions to potential food safety
problems in the future• Undertaken before a problem occurs• Focus
– Foods produced by establishment and related procedures
– Identification of potential food safety problems– Control measures to mitigate potential
problems• Initiated by establishment
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Facility Plan Review• Preemptive solutions to potential food safety
problems in the future• Undertaken before a problem occurs• Focus
– Proposed structural plans and equipment at establishment
– Relation to intended procedures– Functionality, durability, ease of cleaning
• Initiated by establishment
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Food Establishment Regulatory Inspection• Addresses food safety problems occurring today• Routinely scheduled inspections• Focus
– Ongoing processes and procedures– Leading causes of foodborne illness (risk-
based approach)• Initiated by regulatory authority
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Environmental Health Assessment• Addresses food safety issues that occurred in
the past• Occurs in response to a food safety problem • Focuses on (and reconstructs) past events
related to – Implicated food(s)– Prepared/served during outbreak period
• Outbreak investigation team initiates, guided by epidemiologic and laboratory information
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SummaryHACCP/Facility
Plan ReviewRegulatory Inspection
Env’t Health Assessment
When undertaken
Before a food safety problem occurs
Regularly scheduled
Time focus Future Today
Focus of effort
Areas where food safety problems could occur
Ongoing processes focusing on common problems
Who initiates
Food establishment
Regulatory agency
Past
In response to specific problem
Food safety problems related to implicated food during outbreak period
Outbreak inves-tigation team
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Environmental Health Assessment
Objectives:
1. Reconstruct past events, focusing on implicated food(s)
2. Identify contributing factors
3. Identify environmental antecedents
4. Develop effective interventions
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Preparation for Assessment
• Examine available outbreak information– Causative agent– Onset of illness among cases– Likely exposure dates/meals/foods
• Collect food establishment information – Existing regulatory records– Menus, recipes, product formulations– Connection to chain of food establishments
• Review information on causative agent– Reservoirs and previously identified vehicles– Modes of transmission– Likely contributing factors
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Site Visit
Focus on implicated food and time period of outbreak1.Manager interview2.Facility walk through3.Observation of operations4.Collection of samples (food and environment)5.Worker interviews6.Collection of records (and other documents)
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1. Manager Interview
• Work to gain cooperation in investigation• Assess management knowledge and attitude
toward food safety• Collect information about food workers who
prepared the implicated food• Review standard operating procedures
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2. Facility Walk Through
• Get sense of general layout of facility and floor design
• Walk through movement of implicated food through facility
• Identify opportunities for occurrence of relevant contributing factors
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Example Food Flow through Facility
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3. Observation of Operations
• Focus on implicated food and associated processes
• Attempt to reconstruct how food was prepared during period of interest
• Take measurements• Record observations on food preparation
worksheet • Draw flow diagram
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Example Food Preparation WorksheetFOOD PREPARATION REVIEW WORKSHEET
Complaint Number: Establishment Name: _________________________________________________ Address: Phone Number:___________________ Date & Time of Suspect Meal: / : am pm mo day yr Date & Time Food Preparation: / : am pm mo day yr Person Interviewed: Name Position Review: Observing Preparation Interviewing person who made food __Other (specify) Suspect Food: ________________________________________________ DATE
PROCESS
OBSERVATION
AMOUNT
OFFOOD
TIME
OF DAY
TEMP OF
FOOD
EQUIP-MENT USED
DEPTH OF
CONTAINEROR FOOD
THICKNESS
HAND
CONTACT WITH FOOD
WORKER’S
NAME
WORKER’S
HEALTH
OTHER INFO
YN
Ill Well
YN
Ill Well
> Env’t health assessment
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Example Flow DiagramWashed and
chopped
Celery and red pepper from grocery store
Eggs in trays of 32 from Farmer B, stored in walk-
in refrigerator
Eggs boiled for 10 min.
Eggs sliced
Cubed potatoes marinated in
French dressing
Potatoes cooled and
cubed
Potatoes boiled in water until
tender
5 lbs. potatoes washed and
peeled
Potatoes, celery, red
pepper, and eggs mixed gently with
wood spoon
50 lbs. bag of potatoes
from Farmer B
4 cups of mayon-naise added and
stirred into mixture with wooden spoon
Chopped parsley stirred into mixture
Paprika sprinkled
on top
Potato salad placed in resealable container
(cylindrical 8 in. x 14 in.)
Stored in walk-in refrigerator at 4C (39 F) for up to 2
days
Served directly from container onto
customer’s plate with ice cream scoop
Brand Z Paprika from grocery store
Potatoes cooled and parsley washed and
chopped finely
Fresh parsley from grocery store
Celery stored under thawing chicken
Knife used to cut other items cleaned with soapy water at
end of day
Wooden cutting board cleaned with
soapy cloth
Same wooden spoon used to get mayonnaise and all
mixing
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4. Collection of Samples
• Collect food, water, and environmental samples based on suspicions about outbreak source
• Consult with laboratory on collection, storage, and transportation procedures
• Collect as soon as possible and note condition (may store for testing at later time)
> Env’t health assessment
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5. Worker Interviews
• Interview in private• Reconstruct preparation of implicated food
during period of interest• Note unusual circumstances during period of
interest and inconsistencies in the story• Collect information about food worker hygiene
and recent illnesses
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6. Collection of Records
Collect and review • Records that identify source of food or
ingredients (e.g., receipts and invoices)• Worker logs or time cards• Monitoring logs (e.g., temperatures in walk-in
refrigerators)
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Group ExerciseDivide into groups by table.
1.Study the information provided on an outbreak of salmonellosis linked to a restaurant at the end of the module.
2.Walk through the environmental health assessment of the restaurant, answering the questions.
3.Do you see any contributing factors likely to be related to the outbreak?
Time: 15 minutes
Be prepared to share your thoughts with the class.
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Group Exercise (cont’d)An outbreak of gastrointestinal illness is linked to a local restaurant. Seven unrelated restaurant patrons are sick with abdominal pain, nausea, vomiting, and diarrhea. Onset of illness among cases was January 22-24. Two ill patrons had stool specimens positive for Salmonella.
Question 1: You are responsible for undertaking the environmental health assessment. How would you prepare for the investigation?
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Group Exercise (cont’d)The restaurant is known for its burgers but serves a variety of sandwiches and salads. Based on patient interviews, ill persons ate at the restaurant on January 20. All but one ate chicken salad; three ill persons had only chicken salad.
Question 2: What type of activities will you under-take at the facility?
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Group Exercise (cont’d)Question 3: Given the causative agent (Salmonella), implicated food (chicken salad), and setting (food service establishment), what contributory factors will you be looking for?
The manager tells you two employees (Willard and Anita) usually make the salad. Making the chicken salad is a 2-day process. You interview the employees to reconstruct how the salad was made.
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Group Exercise (cont’d)Question 4: Draw a flow diagram for preparing the chicken.
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Group Exercise (cont’d)Question 5: These photos were taken as you ob-served the salad being made. Do any concern you?
1 2 3
4 5 6
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Develop Effective Interventions• Immediate control measures
– Hold– Seize– Cease/desist– License sanctions– Menu limitation
– Embargo– Closure– Worker exclusion
or restrictions– Recalls
• Long term strategies to prevent recurrence– HACCP plan– Risk control plans– Training– Menu/supplier/recipe modifications
> Env’t health assessment
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Traceback Investigation
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Traceback Investigations
• Process used to determine the production and distribution chain of an implicated food
• Purpose:– Identify product so that it can be removed
from further consumption– Determine likely origin of food safety problem– Strengthen epidemiologic associations
between food and illness• Formal regulatory traceback vs. informational
traceback
> Traceback investigation
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Results of Traceback Investigations
Case #1
Case #2-4, 6, 8
Case #5, 7, 13-17
Case #7, 9-12
Grocery Store A
Restaurant A
Cafeteria X
Restaurant B
Deli A
Distributor A
Distributor B
Distributor C
Distributor D
Importer X
Domestic Producer A
Domestic Producer C
Domestic Producer B
Foreign Producer A
Distributor D
Importer X
Domestic Producer B
Domestic Producer C
Foreign Producer A
Domestic Producer A
> Traceback investigation
CASESPOINT OF SERVICE ESTABLISHMENTS
DISBUTORS/IMPORTERS
PRODUCERS/ PROCESSORS
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Role of Local Health Departments
• Undertake scientifically sound investigations to– Implicate specific food item– Rule out end user contamination
• Interview cases for product details and where they purchased the food (e.g., receipts)
• Collect paperwork (e.g., receipts, invoices, shipping documents) from retail food establishments
> Traceback investigation
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Traceforward Investigations
Once source of outbreak identified:•Process used to trace distribution of all implicated lots of food from the original source (not just foods eaten by known cases)•Purpose
– Support recall efforts– Support further case-finding– Test hypothesis about source
> Traceback investigation
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Example
Case #1
Case #3-6
Case #8-17
Grocery Store A
Restaurant A
Cafeteria X
Restaurant B
Distributor A
Distributor B Distributor C Domestic Producer C
Importer X
Foreign Producer A
Domestic Producer A
Domestic Producer B
Case #2
Domestic Producer C
> Traceback investigation
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Example
Case #1
Case #3-6
Case #8-17
Grocery Store A
Restaurant A
Cafeteria X
Restaurant B
Distributor A
Distributor B Distributor C Domestic Producer C
Case #2
Distributor E
Grocery Store C
Deli A
Domestic Producer E
Grocery Store B
Processor A
Cases
Cases
Cases
Domestic Producer D
Domestic Producer F
> Traceforward investigation
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Salmonella Typhimurium and Peanut Butter
• Cluster of S. Typhimurium detected by PulseNet• Studies implicate peanut butter sold to institutions
and peanut butter crackers• Outbreak traced to one plant• Initial recall of specific lots of peanut butter
expanded to include all peanuts and peanut products from implicated plant
• FDA performs traceforward• Ultimately 3,900 products
recalled from several hundred companies
> Traceforward investigation
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Quick Quiz
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Quick Quiz1. Which of the following statements is true about
contributing factors. A. An outbreak will occur if a contributing factor
is present.B. The three major categories of contributing
factors are contamination, survival (lack of inactivation), and proliferation.
C. Contributing factors in an outbreak depend on the causative agent but not the food vehicle or processing method.
D. Correction of the contributing factor will correct the food safety problem and prevent it from occurring again.
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Quick Quiz
2. An environmental health assessment of a food establishment undertaken during an outbreak investigation is similar to a regulatory inspection except it focuses on the past.
A. True
B. False
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Quick Quiz
3. To prepare for an environmental health assessment, the investigator might consult which of the following?
A. Team epidemiologist
B. Laboratory staff
C. Regulatory inspector for facility
D. All of the above
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Quick Quiz
4. All of the following activities might be performed during an environmental health assessment of the implicated facility in an outbreak EXCEPT
A. Interview of the manager of the implicated facility
B. Walk through of the facility
C. Collection of information from ill food workers
D. Observation of all food preparation processes undertaken at the facility
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Quick Quiz5. Staff from local health departments are likely to
be responsible for all of the following activities during a traceback investigation EXCEPTA. Interview of cases for product detailsB. Determining whether contamination at the
food service facility is the source of the outbreak
C. Collection of paperwork from the implicated food establishment
D. Detailed analysis of receipts and invoices