>> Working on an outbreak investigation?
It's important to shift from the mindset of a routine inspector
to an outbreak investigator, so you can understand how
and why the outbreak occurred.
This video reviews the importance
of identifying practices and factors
that contribute to the outbreak.
Finding these contributing factors helps you recommend the
right control measures.
Let's review how outbreaks occur.
When a foodborne illness outbreak is suspected,
the responsible jurisdiction must determine
where in the farm-to-fork continuum the problem occurred.
This continuum includes harvesting, manufacturing,
distribution, and points of final service,
such as a restaurant or someone's home.
The responsible jurisdiction will also investigate the
factors that led to the outbreak.
These are known as contributing factors.
The underlying root causes of these factors are known
as environmental antecedents.
This video will focus
on identifying contributing factors.
Investigators from 3 scientific disciplines are essential
to the investigation: epidemiology, laboratory science,
and environmental health.
These 3 disciplines collect critical information
on the components of the disease triangle.
This information helps the investigators understand the
outbreak, identify practices that contributed to the outbreak,
and recommend actions to control it.
Let's take a closer look at each discipline.
Epidemiologists collect data about the host
of the foodborne illness.
They answer the questions "Who got sick?"
and "When did they get sick?"
Epidemiological data is used to form a hypothesis
on the suspected pathogen or other agent.
The data also help identify implicated food items
that helps guide the investigation.
Laboratory scientists collect data about the agent
that is causing the foodborne illness.
They answer the question "What agent got people sick?"
Environmental health specialists collect data on the environment
that allowed the agent to infect the host.
This information helps answer the questions
"How did the foodborne agent infect the host--
what factors led to that happening?"
And "Why did those factors occur?"
Environmental health specialists use epidemiologic
and laboratory data to guide the environmental assessment.
Identifying the factors that lead to outbreaks
and their underlying causes requires a different approach
and mindset than performing a routine inspection.
An environmental assessment is a systematic process that focuses
on specific foods, processes, and people.
Food safety violations might be identified during the
environmental assessment
that are not associated with the outbreak.
Environmental health specialists must distinguish these general
violations from actual conditions
that led to the outbreak.
While violations not associated with the outbreak are important,
the immediate goal of an environmental assessment
is to identify the specific contributing factors
and their underlying root causes.
Let's take a closer look at these contributing factors.
What exactly are they?
Contributing factors are the factors and practices
that led to the outbreak.
They fall into 3 categories:
contamination, proliferation, and survival factors.
These 3 categories refer to the type of food safety failures
that most likely occurred before the outbreak.
Keep in mind you might identify more
than 1 contributing factor during the investigation.
The first type of contributing factor, contamination,
is when pathogens or other agents get into food.
They can come from many sources, including people,
pests, and the environment.
Contamination can occur
at any point along the farm-to-fork continuum.
One example is when a raw animal product
such as raw chicken cross-contaminates ready-to-eat
food such as salad.
Another example of a contamination factor is
when a sick food worker handles food
with their bare, contaminated hands.
Let's look at the second major category of contributing factors:
proliferation.
Proliferation is when pathogens are growing in the food.
Food that is held, cooled, reheated, or prepared
at the wrong temperatures
for a long time can allow harmful bacteria to grow.
For example, a stock pot of chili is improperly cooled
and held in the temperature danger zone
for hours, allowing Clostridium perfringens to proliferate.
Another example
of a proliferation contributing factor is
when sliced deli meat is held in a refrigerator
for months, allowing Listeria monocytogenes to proliferate.
Our third contributing factor category is survival.
Survival is when pathogens survive a process meant
to kill or reduce them.
Survival contributing factors apply to foods
that require cooking--such as raw beef, pork, and poultry--
to ensure possible pathogens are eliminated
or reduced to safe levels.
One example of a survival factor is
when a hamburger is not cooked
to a hot enough temperature, allowing E. coli
to survive the cooking process.
Another example is sashimi
or raw wild salmon not being frozen long enough
or at the right temperature to ensure parasites are destroyed.
To identify these contributing factors,
the environmental health specialist's role changes
from that of a regulator and inspector to one
of a detective seeking to solve a mystery.
Like a detective,
the environmental health specialist gathers clues
and uses them to determine how and why the outbreak happened.
Remember: outbreak investigations differ
from routine inspections.
The environmental assessment piece
of the outbreak investigation looks at the big picture
to identify what led to a breakdown
in food safety, while routine inspection focus more
on violations.
And while the environmental assessment focuses
on food safety issues that may have occurred in the past,
an inspection is a snapshot
of current food safety practices and conditions.
Identifying contributing factors should be based
on information gathered during the environmental assessment,
not the results of routine inspections.
Most of these assessments require multiple site visits
as more information is made available
about the suspected agent and implicated food items.
Let's look at some common activities
in the environmental assessment piece
of the outbreak investigation.
Investigators visit the location to see how food is prepared
and review food flows for implicated food.
Observations should concentrate on the specific processes
or practices that could have contributed
to the contamination, survival, or proliferation
of the suspected agent.
As part of the environmental assessment,
investigators also interview managers and food workers.
Since it's not possible to observe what actually happened
in the past, the goal of interviewing is
to piece together the events that occurred at the time
of the exposure and develop insights into the factors
that led to a foodborne illness outbreak
and also the root causes.
Investigators often review or collect records
to understand what happened in the past.
Records can include invoices, employee sick logs,
employee schedules, recipes,
and customer information for case finding.
Investigators take samples of the environment
or implicated food to be tested for pathogens or other agents,
as they still could be present and available to test.
For every identified contributing factor,
the environmental specialist must try
to understand why the contributing factor occurred.
These root causes are directly related to the conditions
in the food establishment: the people, equipment, food,
processes, and economics.
Once the contributing factors are identified, it's important
to use this information to recommend
and implement effective, sustainable control measures.
Control measures are actions or activities that are taken
to prevent, eliminate, or reduce the occurrence
of an identified hazard.
Control measures can be short-term
and immediately implemented,
such as discarding potentially contaminated food.
Other control measures may be long-term,
such as requiring training
or changing a preparation procedure.
Both short- and long-term control measures are critical
for stopping an outbreak and preventing it
from happening again at a specific location.
Implementing appropriate control measures requires accurately
identifying both contributing factors
and their underlying root causes.
We hope you have gained an understanding
of some basic information about contributing factors:
what they are, how they are identified,
and how they can be used
to develop effective control measures.
For more food safety resources
for environmental health practitioners,
go to cdc.gov/nceh/ehs/food.