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Understanding Foodborne Disease Outbreaks
Using Environmental Assessments: The
Importance of Antecedents to Contributing
Factors
Vincent J. Radke, MPH, RS, CP-FS, DAAS, CPH
Sanitarian
Centers for Disease Control and Prevention
Sixth International Conference on Food Safety
Dubai, 2011
National Center for Environmental Health
Environmental Health Services Branch
Definitions

Environmental Assessment
 The component of an outbreak investigation that fully
describes how the environment contributed to the
introduction and or transmission of agents that cause
illness. Environment is everything external to the host,
including air, food, water, animals, plants, climate, etc as
well as people, social and built environments. All aspects
of the external environment can be listed as variables that,
in relation to transmission, are neutral, conducive or
protective. From this description contributing factors and
environmental antecedents to an outbreak can be
determined.
 NOT an inspection
Definitions

Contributing Factors
 The factors likely to be conducive to the contamination and survival
of the etiologic agent or suspected agent and/or to its growth or
proliferation.
• Contamination Factors (C1-15)
o
Toxic substance part of the tissue , Contaminated raw product, Cross-contamination of
ingredients , Bare-hand contact by a food handler/worker/preparer who is suspected to
be infectious
• Proliferation Factors (P1-12)
o
Improper cold holding due to malfunctioning refrigeration equipment, Improper hot
holding due to improper procedure or protocol, Prolonged cold storage
• Survival Factors (S1-4)
o
Insufficient time and/or temperature during cooking/heat processing , Insufficient time
and/or temperature during reheating
Definitions

Environmental Antecedents
 Root causes
 Supporting factor(s) to the contamination, survival or increase of
biological or chemical agents in food
 They may be related to
•
•
•
•
•
•
•
People
Equipment
Process
Food
Economics
Behavior
Other circumstances
EXAMPLE

What caused the outbreak? Campylobacter Jejuni (CJ)
in the “cooked” chicken (EPI, LAB, ENV Assessment)

Why was CJ in the “cooked" chicken? Insufficient
temperature during cooking to kill CJ (Contributing
Factor)

Why was there insufficient temperature during the
cooking process to kill CJ? The cook did not know the
temperature (Environmental Antecedent)
Environmental Assessments

Describes how the environment contributes to the
introduction and or transmission of agents that cause
illness

Objectives of the assessment
• Identify contributing factors
• Identify environmental antecedents
• Generate recommendations for informed interventions
Relationship of Environmental Antecedents to
Contributing Factors
Outbreak
Contamination at preparation step
Contributing
Factor A
Bare-hand contact by a food handler/worker/preparer
who is suspected to be infectious
Handling after kill step
No kill step
Multiple steps involving process
No sick leave
Afraid of reporting
No policy
No supervision
Lack of knowledge
Hands not washed
No gloves used
PEOPLE
PROCESS
Minimum wage
Lack of hand wash sinks
Location of hand wash sinks
Lack of supplies for hand wash sinks
No supervision
Not enough water available
Not enough gloves available
Equipment costs
Glove costs
ECONOMICS
FOOD
EQUIPMENT
Contributing
Factor X
Past
Foodborne Illness
Outbreak Environmental
Assessment
Present
Routine Regulatory
Inspections
Future
Physical Facility Plan
Review
HACCP Plan Development
Using Environmental Assessments to
Investigate Disease Outbreaks
No
illness
Contributing
Factors
Protective
System
Medium
(food, water,
Wastewater,
Air, etc.)
Adverse
Health Outcomes
Exposure
Process
Equipment
People
Economics
Environmental Antecedents
Environmental
Health
Assessment
Epidemiology
Lab
(Identify
and/or
confirm
Agent)
Increasing
Severity of
illness
Outbreak
EHS-Net

Environmental Health Specialist Network

Pronounced “S – Net”

www.cdc.gov/nceh/ehs/EHSNet/default.htm
Study
Introduction




Foodborne outbreaks investigations represent one
aspect of the overall foodborne disease surveillance
system
Environmental assessments of investigations provide
food safety programs with better understanding of
contributing factors and environmental assessments
While contributing factors are sometimes captured
these factors are not framed in the context within
which they occurred
Environmental antecedents help provide a meaningful
context for contributing factors
Purpose

The purpose of this study was to identity contributing
factors to foodborne illness outbreaks in food service
establishments (restaurants, delis, schools, etc) and to
describe the characteristics, policies, and practices
(possible environmental antecedents) of these
establishments via environmental assessments
Methods



The study was conducted by the Environmental Health
Specialists Network (EHS-Net). EHS-Net is a
collaborative project of CDC, USFDA, USDA and nine
states ( CA, CT, GA, IA, MN, NY, OR, RI, TN)
Descriptive study to collect information on
contributing factors and antecedents (food handling
policies and practices)
Data collection based on interview with a kitchen
manager, observations in the kitchen, development of a
food flow of the suspected or identified vehicle, and
sometimes re-enactment of the food handling practices
used for the vehicle
Methods
(Cont.)


Descriptive analysis of the data set included univarate
frequencies and cross-tabulations for selected
variables
Future analysis to include test for association using chisquare and t-test, we may use regression modeling to
examine any multivariate relationships and to control
for confounding
Results




154 environmental assessments conducted ( June,
2006 to September , 2007)
Of those outbreaks with an identified etiology (102) 33
(30%) were bacterial and 69 (63%) viral
84% were identified as complex; 13% were cook serve;
3 % were prep serve
Spanish was the primary language of 58% of the food
workers but only 41% of the mangers could speak
Spanish
Results
(Cont.)



95% of establishments had floor cleaning policies (37%
of these were written BUT fewer had policies for
cleaning food contact surfaces (food slicers 72%). In
these establishments 33% had a written policy for
cleaning food slicers.
More managers received paid sick leave (66%) than
workers (40%)
Establishments physical characteristics potentially
related to safe food handling practices such as hand
sinks availability revealed the majority of
establishments had hand washing sinks in the
restroom (96%)
Results
(Cont.)

Also a majority of establishments had hand washing
sinks available in the work areas (94%). Hands free
operated hand washing sinks were rare, found in only
4% of employee restrooms and 3% of work areas
Conclusions


The environmental assessment in a foodborne
outbreak investigation is critical to understanding
contributing factors and potential antecedents to
foodborne illness, yet information regarding potential
antecedents is rarely captured.
While current foodborne outbreak surveillance data
may identify working while ill or poor handwashing
practices as factors contributing to outbreaks
information on why these circumstances may have
existed is not collected or reported.
Conclusions
(Cont.)

A systematic collection, analysis, interpretation, and
dissemination of environmental data from foodborne
disease outbreak investigations can support the overall
foodborne disease surveillance system in a country,
strengthening the ability of food control authorities at
all levels of government to formulate food safety action
and assess the effectiveness of these actions.
Vince Radke
[email protected]
www.cdc.gov
Thank you
Questions
For more information please contact Centers for Disease Control and Prevention
1600 Clifton Road NE, Atlanta, GA 30333
Telephone, 1-800-CDC-INFO (232-4636)/TTY: 1-888-232-6348
E-mail: [email protected]
Web: www.cdc.gov
The findings and conclusions in this report are those of the authors and do not necessarily represent the official position of
the Centers for Disease Control and Prevention.
National Center for Environmental Health
Environmental Health Services Branch